Revert "MIPS: page.h: Provide more readable definition for PAGE_MASK."

This reverts commit c17a6554782ad531f4713b33fd6339ba67ef6391.

Manuel Lauss writes:

lmo commit c17a6554 (MIPS: page.h: Provide more readable definition for
PAGE_MASK) apparently breaks ioremap of 36-bit addresses on my Alchemy
systems (PCI and PCMCIA) The reason is that in arch/mips/mm/ioremap.c
line 157  (phys_addr &= PAGE_MASK) bits 32-35 are cut off.  Seems the
new PAGE_MASK is explicitly 32bit, or one could make it signed instead
of unsigned long.
Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus

Pull MIPS fix from Ralf Baechle:
 "Revert the change of the definition of PAGE_MASK which was prettier
  but broke a few relativly rare platforms"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
  Revert "MIPS: page.h: Provide more readable definition for PAGE_MASK."