xfs: fix incorrect return type for fsdax fault handlers

The kernel robot complained about this:

>> fs/xfs/xfs_file.c:1266:31: sparse: sparse: incorrect type in return expression (different base types) @@     expected int @@     got restricted vm_fault_t @@
   fs/xfs/xfs_file.c:1266:31: sparse:     expected int
   fs/xfs/xfs_file.c:1266:31: sparse:     got restricted vm_fault_t
   fs/xfs/xfs_file.c:1314:21: sparse: sparse: incorrect type in assignment (different base types) @@     expected restricted vm_fault_t [usertype] ret @@     got int @@
   fs/xfs/xfs_file.c:1314:21: sparse:     expected restricted vm_fault_t [usertype] ret
   fs/xfs/xfs_file.c:1314:21: sparse:     got int

Fix the incorrect return type for these two functions.

While we're at it, make the !fsdax version return VM_FAULT_SIGBUS
because a zero return value will cause some callers to try to lock
vmf->page, which we never set here.

Fixes: ea6c49b7 ("xfs: support CoW in fsdax mode")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/xfs_file.c

@@ -1261,7 +1261,7 @@ xfs_file_llseek(
 }
 
 #ifdef CONFIG_FS_DAX
-static int
+static inline vm_fault_t
 xfs_dax_fault(
 	struct vm_fault		*vmf,
 	enum page_entry_size	pe_size,
@@ -1274,14 +1274,15 @@ xfs_dax_fault(
 				&xfs_read_iomap_ops);
 }
 #else
-static int
+static inline vm_fault_t
 xfs_dax_fault(
 	struct vm_fault		*vmf,
 	enum page_entry_size	pe_size,
 	bool			write_fault,
 	pfn_t			*pfn)
 {
-	return 0;
+	ASSERT(0);
+	return VM_FAULT_SIGBUS;
 }
 #endif