drm/amdgpu: add gfx9 gpr EDC workaround when RAS is enabled

When RAS is enabled, initializes the VGPRs/LDS/SGPRs and
resets EDC error counts. This is done in late_init, before
RAS TA GFX enable.

Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>