rdma: fix build errors on s390 and MIPS due to bad ZERO_PAGE use

The parameter to ZERO_PAGE() was wrong, but since all architectures
except for MIPS and s390 ignore it, it wasn't noticed until 0-day
reported the build error.

Fixes: 67f269b3 ("RDMA/ucontext: Fix regression with disassociate")
Cc: stable@vger.kernel.org
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/infiniband/core/uverbs_main.c

@@ -895,7 +895,7 @@ static vm_fault_t rdma_umap_fault(struct vm_fault *vmf)
 
 	/* Read only pages can just use the system zero page. */
 	if (!(vmf->vma->vm_flags & (VM_WRITE | VM_MAYWRITE))) {
-		vmf->page = ZERO_PAGE(vmf->vm_start);
+		vmf->page = ZERO_PAGE(vmf->address);
 		get_page(vmf->page);
 		return 0;
 	}