- main_ram mem_map is now directly used by add_sdram when origin is None.
- max_sdram_size/min_l2_data_width are no longer exposed as targets arguments this can
still be used enforced directly in the few cases it is useful.

boards: Add Vendor prefix to platforms/targets name when useful and when multiple boards from the same vendor. (With Retro-Compat on the imports).

targets: Switch to soc_core_args/soc_core_argdict (instead of soc_sdram that is now deprecated, but still supported for now).

Collect --with-ethernet/--with-etherbone, --with-spi-sdcard/--with-sdcard,
etc. into ArgumentParser.add_mutually_exclusive_group()s.  That way, we
get pretty --help output, and appropriate error messages if somebody
tries to ask for something that doesn't make sense.

The SoC reset added recently creates a path between sys_clk and pll.clkin
clock domains that is reported by the tools but that can be safely ignored.

targets/pcie: simplify using new LiteX's add_pcie method and enable it on all devices supported by LitePCIe.

targets/pcie: remove force of csr_data_width to 32 (this is now the default) but just add a check on the pcie block.

targets/xilinx: use generic name for idelay clk (avoid clk200, clk400, etc...) since we somtimes want to change it.

Moved platform call inside of BaseSoC init for compatibility with linux-on-litex-vexriscv support. Added optional spi-sdcard support over P2 header.

DNA/XADC/ICAP are demonstrated in LitePCIe repository and should probably be added with
a add_xy method.

targets/acorn_cle_215: use new generate_litepcie_software functions and add --driver argument to generate driver.

targets/acorn_cle_215: automatically copy software from litepcie and generate headers in kernel directory.

Default to Chaser mode and similar user interface than GPIOOut.