ACPI: Allow setting SCI_EN bit in PM1_CONTROL register

This is needed by at least the Mac Mini's, which (incorrectly) come back
from suspend with SCI_EN clear.

Thanks to Frédéric Riss for hunting this down.

Acked-by: Frédéric Riss <frederic.riss@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Len Brown <len.brown@intel.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>