Display Core support for DCN 3.1.4

v2:(squash)fix non-x86 in dc/dcn314/Makefile
Properly handle PPC as well. (Alex)
v3: minor cleanup (Alex)
v4: fix comment (Alex)
Signed-off-by: Roman Li <roman.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>