drm/amd/amdgpu: Add GFX9.1 PWR_MISC_CNTL_STATUS register to headers

The registers are needed for umr and not in the headers.  I left them
in the gfx_v9_0.c since it includes 9.0 and 9.4 headers and including
9.1 headers would result in a lot of duplicate registers clashing.

Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>