baytrail: add GPIO SMI support

GPIOs which trigger SMIs only set the status bits in the ALT_GPIO_SMI
regier. No bits in the SMI_STS register are set. Therefore, the
ALT_GPIO_SMI register needs to be read and cleared on every SMI.
Additionally, the mainboard_gpi_smi() handler needs to be called as
well on every SMI because of this property.

BUG=chrome-os-partner:23505
BRANCH=None
TEST=Built and booted to recovery screen. Typed 'lidclose' on EC
     console. SMI occurred which caused the board to be shutdown.

Change-Id: Ic204d8b928a0cb4f51f108a649f374d9f94e4f47
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/176391
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: http://review.coreboot.org/4958
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
4 files changed