btrfs: use DIV_ROUND_UP instead of open-coded variants

The form

  (value + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT

is equivalent to

  (value + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE

The rest is a simple subsitution, no difference in the generated
assembly code.

Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
index dfad851..78285f3 100644
--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -266,8 +266,7 @@
 	char *data_in;
 	unsigned long page_in_index = 0;
 	unsigned long page_out_index = 0;
-	unsigned long total_pages_in = (srclen + PAGE_CACHE_SIZE - 1) /
-					PAGE_CACHE_SIZE;
+	unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_CACHE_SIZE);
 	unsigned long buf_start;
 	unsigned long buf_offset = 0;
 	unsigned long bytes;