PM/ACPI/x86: Fix sparse warning in arch/x86/kernel/acpi/sleep.c

One of the numbers in arch/x86/kernel/acpi/sleep.c is long, but it is
not annotated appropriately, so sparese warns about it.  Fix that.

[rjw: added the changelog.]

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>