[POWERPC] add clrsetbits macros

This patch adds the clrsetbits_xxx() macros, which are used to set and clear
multiple bits in a single read-modify-write operation.  Specify the bits to
clear in the 'clear' parameter and the bits to set in the 'set' parameter.
These macros can also be used to set a multiple-bit bit pattern using a mask,
by specifying the mask in the 'clear' parameter and the new bit pattern in the
'set' parameter.  There are big-endian and little-endian versions for 8, 16,
32, and 64 bits.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>