xarray.h: correct return code documentation for xa_store_{bh,irq}()

__xa_store() and xa_store() document that the functions can fail, and
that the return code can be an xa_err() encoded error code.

xa_store_bh() and xa_store_irq() do not document that the functions can
fail and that they can also return xa_err() encoded error codes.

Thus: Update the documentation.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Link: http://lkml.kernel.org/r/20200430111424.16634-1-manfred@colorfullife.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/xarray.h

@@ -576,7 +576,7 @@ void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
  *
  * Context: Any context.  Takes and releases the xa_lock while
  * disabling softirqs.
- * Return: The entry which used to be at this index.
+ * Return: The old entry at this index or xa_err() if an error happened.
  */
 static inline void *xa_store_bh(struct xarray *xa, unsigned long index,
 		void *entry, gfp_t gfp)
@@ -602,7 +602,7 @@ static inline void *xa_store_bh(struct xarray *xa, unsigned long index,
  *
  * Context: Process context.  Takes and releases the xa_lock while
  * disabling interrupts.
- * Return: The entry which used to be at this index.
+ * Return: The old entry at this index or xa_err() if an error happened.
  */
 static inline void *xa_store_irq(struct xarray *xa, unsigned long index,
 		void *entry, gfp_t gfp)