This patch is to add the files of NBIO v7.7 block.
NBIO (New Bus IO) is the block which handles
the GPU interface to the PCIe bus.

v2: squash in register name fix (Xiaojian)
Signed-off-by: Xiaojian Du <Xiaojian.Du@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>