drm/xe: Pick correct userptr VMA to repin on REMAP op failure

drm/xe: Pick correct userptr VMA to repin on REMAP op failure

A REMAP op is composed of 3 VMA's - unmap, prev map, and next map. When
op_execute fails with -EAGAIN we need to update the local VMA pointer to
the current op state and then repin the VMA if it is a userptr.

Fixes a failure seen in xe_vm.munmap-style-unbind-userptr-one-partial.

Fixes: b06d47be7c83 ("drm/xe: Port Xe to GPUVA")
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240201004849.2219558-3-matthew.brost@intel.com