power management: implement pm_ops.valid for everybody

Almost all users of pm_ops only support mem sleep, don't check in .valid and
don't reject any others in .prepare so users can be confused if they check
/sys/power/state, especially when new states are added (these would then
result in s-t-r although they're supposed to be something different).

This patch implements a generic pm_valid_only_mem function that is then
exported for users and puts it to use in almost all existing pm_ops.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: linux-pm@lists.linux-foundation.org
Cc: Len Brown <lenb@kernel.org>
Acked-by: Russell King <rmk@arm.linux.org.uk>
Cc: Greg KH <greg@kroah.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/pm.h

@@ -128,6 +128,9 @@ typedef int __bitwise suspend_disk_method_t;
  *	always valid and never passed to this call.
  *	If not assigned, all suspend states are advertised as valid
  *	in /sys/power/state (but can still be rejected by prepare or enter.)
+ *	Since new states can be added for other platforms, you should
+ *	assign this callback. There is a %pm_valid_only_mem function
+ *	available if you only implemented mem sleep.
  *
  * @prepare: Prepare the platform for the given suspend state. Can return a
  *	negative error code if necessary.
@@ -165,6 +168,7 @@ extern void pm_set_ops(struct pm_ops *pm_ops);
 extern struct pm_ops *pm_ops;
 extern int pm_suspend(suspend_state_t state);
 
+extern int pm_valid_only_mem(suspend_state_t state);
 
 /**
  * arch_suspend_disable_irqs - disable IRQs for suspend