drm/amd/display: Read resource_straps from registers for DCE12

Now that the registers exist, assign them to the resource_straps struct.

v2: Fix indentation
v3: Fix trailing whitespace and checkpatch warnings.

bug: https://bugs.freedesktop.org/show_bug.cgi?id=103404
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>