soc/intel/apollolake: Add handler for SCI

soc/intel/apollolake: Add handler for SCI

This patch adds the handler to enable bit for gpio_tier1_sci_en.
gpio_tier1_sci_en enables the setting of the GPIO_TIER1_SCI_STS
bit to generate a wake event and/or an SCI or SMI#. We are setting
the bit for gpio_tier1_sci_en from the ASL code as OS clears this bit
if set from BIOS. As per ACPI spec _GPE is defined as the Named
Object  that evaluates to either an integer or a package. If _GPE
evaluates to an integer, the value is the bit assignment of the SCI
interrupt within the GPEx_STS register of a GPE block described in
the FADT that the embedded controller will trigger. FADT right now
has no mechanism to acheive the same.

Change-Id: I1e1bd3f5c89a5e6bea2d1858569a9d30e6da78fe
Signed-off-by: Shaunak Saha <shaunak.saha@intel.com>
Reviewed-on: https://review.coreboot.org/15578
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>