drm/amdgpu: add fbdev suspend/resume on gpu reset

This can fix the baco reset failure seen on Navi10.
And this should be a low risk fix as the same sequence
is already used for system suspend/resume.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>