drm/amd/amdgpu: Remove static from variable in RLCG Reg RW

[why]
These static variables save the RLC Scratch registers address.
When we install multiple GPUs (for example: XGMI setting) and
multiple GPUs call the function at same time. The RLC Scratch
registers address are changed each other. Then it caused
reading/writing from/to wrong GPU.

[how]
Removed the static from the variables. The variables are
on the stack.

Fixes: 5d447e29 ("drm/amdgpu: add helper for rlcg indirect reg access")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Gavin Wan <Gavin.Wan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>