Unlike WREG32_P() it understands offsets/masks and doesn't
require the caller to shift the value (or mask properly).
It's applied where suitable in the gfx_v8_0.c driver to start
with.
Signed-off-by: Tom St Denis <tom.stdenis@amd.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>