percpu: update free path with correct new free region

When updating the chunk's contig_hint on the free path of a hint that
does not touch the page boundaries, it was incorrectly using the
starting offset of the free region and the block's contig_hint. This
could lead to incorrect assumptions about fit given a size and better
alignment of the start. Fix this by using (end - start) as this is only
called when updating a hint within a block.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Peng Fan <peng.fan@nxp.com>

mm/percpu.c

@@ -871,7 +871,7 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
 		pcpu_chunk_refresh_hint(chunk);
 	else
 		pcpu_chunk_update(chunk, pcpu_block_off_to_off(s_index, start),
-				  s_block->contig_hint);
+				  end - start);
 }
 
 /**