parisc: asm/pdc.h should include asm/page.h

Fixes this build error:
arch/parisc/kernel/pdc_cons.c:117: error: '__PAGE_OFFSET' undeclared

Signed-off-by: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>