nouveau: return -EBUSY when hmm_range_wait_until_valid fails

-EAGAIN has a magic meaning for non-blocking faults, so don't overload it.
Given that the caller doesn't check for specific error codes this change
is purely cosmetic.

Link: https://lore.kernel.org/r/20190724065258.16603-6-hch@lst.deTested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/gpu/drm/nouveau/nouveau_svm.c

@@ -502,7 +502,7 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range)
 
 	if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
 		up_read(&range->vma->vm_mm->mmap_sem);
-		return -EAGAIN;
+		return -EBUSY;
 	}
 
 	ret = hmm_range_fault(range, true);