soc/interconnect: remove axi_lite

soc/interconnect: remove axi_lite

axi_lite code was defining AXI4Lite signals and doing a AXI4Lite bridge to the
CSR bus when LiteX was not having proper AXI support. LiteX now has  proper AXI
support and it also cover what axi_lite was doing: To create a AXILite to CSR
bus, user can create an AXILite2Wishbone bridge and then connect the CSR bus
directly to the wishbone bus as done in the others non-AXI SoC.