netfilter: bitwise: rename some boolean operation functions

In the next patch we add support for doing AND, OR and XOR operations
directly in the kernel, so rename some functions and an enum constant
related to mask-and-xor boolean operations.

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>