swsusp: use inline functions for changing page flags

Replace direct invocations of SetPageNosave(), SetPageNosaveFree() etc.  with
calls to inline functions that can be changed in subsequent patches without
modifying the code calling them.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>