gpu: host1x: check relocs after all gathers are consumed

The num_relocs count are passed to the kernel per job, not per gather.

For multi-gather jobs, we would previously fail if there were relocs in
other gathers aside from the first one.

Fix this by simply moving the check until all gathers have been
consumed.

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Reviewed-by: Arto Merilainen <amerilainen@nvidia.com>
Acked-By: Terje Bergstrom <tbergstrom@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>