- Use memchr_inv to check if the data contains all 0xFF bytes.
  It is faster than looping for each byte.

- Use memcmp to compare memory areas
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>