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 --cc fs/btrfs/check-integrity.c
Simple merge

diff --cc fs/btrfs/compression.c
Simple merge

diff --cc fs/btrfs/file.c
Simple merge

diff --cc fs/btrfs/free-space-cache.c
Simple merge

diff --cc fs/btrfs/ioctl.c
Simple merge

diff --cc fs/btrfs/lzo.c
Simple merge

diff --cc fs/btrfs/raid56.c
Simple merge

diff --cc fs/btrfs/zlib.c
Simple merge