drm/amdgpu: always backup and reemit fences

drm/amdgpu: always backup and reemit fences

If when we backup the ring contents for reemit before a
ring reset, we skip jobs associated with the bad
context, however, we need to make sure the fences
are reemited as unprocessed submissions may depend on
them.

v2: clean up fence handling, make helpers static

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 155a748f14bc0b72783994dea7c5a12276730342)