[hw] Split DV and DD for lowRISC vendored IPs

[martin-velay]

This would allow us to pull in the upstream DV files while maintmaining the DD files in the same state as before. This is needed as some RTL changes are not desired while we need to get latest DV changes from upstream. This will work until the DV diverge from the DD. Then, another solution will be needed to keep the DV and DD in sync (maybe cherry- picking individual changes in an OpenTitan fork dedicated to Mocha which will be manually maintained for Mocha needs).

[martin-velay]

All looks good now:

dvsim hw/top_chip/dv/mocha_sim_cfgs.hjson -i smoke --reseed 1
...
|                                              Name                                               |  Passing  |  Total  |  Pass Rate  |  Coverage  |
|:-----------------------------------------------------------------------------------------------:|:---------:|:-------:|:-----------:|:----------:|
|                     [UART](scratch/split_dd_dv_opentitan/reports/uart.html)                     |     3     |    3    |  100.00 %   |     --     |
|            [SPI_DEVICE_2P](scratch/split_dd_dv_opentitan/reports/spi_device_2p.html)            |     3     |    3    |  100.00 %   |     --     |
|                 [SPI_HOST](scratch/split_dd_dv_opentitan/reports/spi_host.html)                 |     3     |    3    |  100.00 %   |     --     |
|                 [RV_TIMER](scratch/split_dd_dv_opentitan/reports/rv_timer.html)                 |     3     |    3    |  100.00 %   |     --     |
|               [PRIM_ALERT](scratch/split_dd_dv_opentitan/reports/prim_alert.html)               |     2     |    2    |  100.00 %   |     --     |
|                 [PRIM_ESC](scratch/split_dd_dv_opentitan/reports/prim_esc.html)                 |     1     |    1    |  100.00 %   |     --     |
|                [PRIM_LFSR](scratch/split_dd_dv_opentitan/reports/prim_lfsr.html)                |     2     |    2    |  100.00 %   |     --     |
|   [ENTROPY_SRC_RNG_16BITS](scratch/split_dd_dv_opentitan/reports/entropy_src_rng_16bits.html)   |     3     |    3    |  100.00 %   |     --     |
|                      [I2C](scratch/split_dd_dv_opentitan/reports/i2c.html)                      |     3     |    3    |  100.00 %   |     --     |
|            [KMAC_UNMASKED](scratch/split_dd_dv_opentitan/reports/kmac_unmasked.html)            |     3     |    3    |  100.00 %   |     --     |
|                [XBAR_PERI](scratch/split_dd_dv_opentitan/reports/xbar_peri.html)                |     1     |    1    |  100.00 %   |     --     |
|                     [GPIO](scratch/split_dd_dv_opentitan/reports/gpio.html)                     |     4     |    4    |  100.00 %   |     --     |
|                   [PWRMGR](scratch/split_dd_dv_opentitan/reports/pwrmgr.html)                   |     3     |    3    |  100.00 %   |     --     |
|                   [RSTMGR](scratch/split_dd_dv_opentitan/reports/rstmgr.html)                   |     3     |    3    |  100.00 %   |     --     |
|            [ROM_CTRL_32KB](scratch/split_dd_dv_opentitan/reports/rom_ctrl_32kb.html)            |     3     |    3    |  100.00 %   |     --     |
| [RV_DM_USE_JTAG_INTERFACE](scratch/split_dd_dv_opentitan/reports/rv_dm_use_jtag_interface.html) |     0     |    7    |   0.00 %    |     --     |
|            [TOP_MOCHA_SIM](scratch/split_dd_dv_opentitan/reports/top_mocha_sim.html)            |    30     |   34    |   88.24 %   |     --     |