X60/T60: fix return value of mainboard_io_trap_handler()

X60/T60: fix return value of mainboard_io_trap_handler()

The handler should return 1 if it handled the request. The current
code returns 0, which causes 'Unknown function' logs.

Change-Id: Ic296819a5f8c6f1f97b7d47148182226684882a0
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Reviewed-on: http://review.coreboot.org/29
Tested-by: build bot (Jenkins)