drm/amdgpu: Improve RAS documentation (v2)

Clarify some areas, clean up formatting, add section for
unrecoverable error handling.

v2: fix grammatical errors

Reviewed-by: Yong Zhao <yong.zhao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
2 files changed