testing: add packet printing helper function
testing: add rx loopback
proto FW: use memory buffer for tx and rx
proto FW: use byteoder crate to handle endianness
proto FW: add event packet reader and writer
proto FW: add error correction for 4x char
zc706: add fmc pads
zc706: add constraint to fix comma alignment & setup/hold time issue
zc706: add csr & mem group for cxp
zc706: add CXP to rtio_channel
testing: add txusrclk mmcm & loopback mode
testing: add debug output
testing: send comma in the middle of long packet to maintain lock
downconn: don't put IDLE into fifo
downconn: add GTX and QPLL support
downconn: add DRP for GTX and QPLL to support all CXP linerates
GTX: add gtx with mmcm for TXUSRCLK freq requirement
GTX: add loopback mode parameter for testing
GTX: add gtx with 40bits internal width
GTX: use built-in comma aligner
GTX: add comma checker to ensure comma is aligner on highest linerate
GTX: set QPLL as CLK source for GTX