drm/amdgpu: Remove volatile from RLC files

drm/amdgpu: Remove volatile from RLC files

The RLC uses volatile with some pointers that are not directly related
to any of the situations where volatile is advised to be used [1]. For
this reason, this commit removes all the volatile occurrences associated
with RLC.

1. https://docs.kernel.org/process/volatile-considered-harmful.html

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Rodrigo Siqueira <siqueira@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>