[PATCH] sh: Use pfn_valid() for lazy dcache write-back on SH7705

SH7705 in extended cache mode has some left-over VALID_PAGE() cruft that it
checks when doing lazy dcache write-back.  This has been gone for some time
(the last bits were in the discontig code, which should now also be gone --
this also fixes up a build error in the non-discontig case).

pfn_valid() gives the desired behaviour, so we switch to that.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>