arm: rename BIT_{WORD/MASK/PER_WORD) to BITOP_*

arm: rename BIT_{WORD/MASK/PER_WORD) to BITOP_*

So BIT_WORD can be imported from Linux. The difference between current
Linux implementation of BIT_WORD is that the size of the word unit is
a long integer, while the Xen one is hardcoded to 32 bits.

Current users of BITOP_WORD on Arm (which considers a word a long
integer) are switched to use the generic BIT_WORD which also operates
on long integers.

No functional change intended.

Suggested-by: Julien Grall <julien@xen.org>
Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Julien Grall <julien@xen.org>