drm/radeon: make missing smc ucode non-fatal (r7xx-SI)

Prevent driver load problems if the smc is missing.

bug:
https://bugzilla.kernel.org/show_bug.cgi?id=63011

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Mikko Rapeli <mikko.rapeli@iki.fi>
Cc: stable@vger.kernel.org

diff --cc drivers/gpu/drm/radeon/ni.c
Simple merge

diff --cc drivers/gpu/drm/radeon/r600.c
Simple merge

diff --cc drivers/gpu/drm/radeon/si.c
Simple merge