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
GTX: add multilane rx support with the same rx reseter
