PM: Make suspend_ops static

The variable suspend_ops representing the set of global platform-specific
suspend-related operations, used by the PM core, need not be exported outside
of kernel/power/main.c .   Make it static.

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>