drm/amdgpu: No sysfs, not an error condition

Not being able to create amdgpu sysfs attributes
is not a fatal error warranting not to continue
to try to bring up the display. Thus, if we get
an error trying to create amdgpu sysfs attrs,
report it and continue on to try to bring up
a display.

Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Slava Abramov <slava.abramov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>