x86: Add iMac9,1 to pci_reboot_dmi_table

On the iMac9,1 /sbin/reboot results in a black mangled screen. Adding
this DMI entry gets the machine to reboot cleanly as it should.

Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
LKML-Reference: <1266362249-3337-1-git-send-email-justinmattock@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>