rtc-cmos: make it load on PNPBIOS systems

Replace CONFIG_PNPACPI with CONFIG_PNP, so it loads on ACPI-less PNPBIOS
systems.

Signed-off-by: Marko Vrh <mvrh@freeshells.ch>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>