Support for the RHS Research LiteFury

LiteFury is an Artix-7 development board in the M.2 form factor
for PCIe accelerator development. It's similar to the Aller but
with an xc7a100t rather than an xc7a200t and no TPM module.

https://rhsresearch.com/collections/rhs-public/products/litefury

Pinout from https://github.com/360nosc0pe project.

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

add Qmtech EP4CE15 coreboard support

ex of use:
./simple.py litex_boards.platform.ulx3s --build --load
./simple.py litex_boards.platform.trellisboard --build --load
./simple.py litex_boards.platform.arty --build --load
etc...

Required to simplify simple.py target and use trellis/icestorm as default toolchain.

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

Lattice NX PLL Support

Add LFE5U-12F device for ULX3S