[PARISC] Kill off ASM_PAGE_SIZE use

We have the macro _AC() generally available now
so the calculation of PAGE_SIZE can be made
assembler compatible.
Introduce use of _AC() and kill all users of
ASM_PAGE_SIZE.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>