Split out apm register emulation for acpi.c into apm.c.
The apm emulation will be used later.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>