drm/amdgpu: clean up ras sysfs creation (v2)

Merge ras sysfs creation together by calling sysfs_create_group
once, as sysfs_update_group may not work properly as expected.

v2: improve commit message

Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Dennis Li <Dennis.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>