swsusp: remove code duplication between disk.c and user.c

swsusp: remove code duplication between disk.c and user.c

Currently, much of the code in kernel/power/disk.c is duplicated in
kernel/power/user.c , mainly for historical reasons.  By eliminating this code
duplication we can reduce the size of user.c quite substantially and remove
the maintenance difficulty resulting from it.

[[email protected]: kernel/power/disk.c: make code static]
Signed-off-by: Rafael J. Wysocki <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Cc: Nigel Cunningham <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>