soc/intel/apollolake: Add function to read and clear GPE status

Implement the generic acpi_get_gpe() function to read and clear
the GPE status for a specific GPE.

Tested by watching GPE status in a loop while generating interrupts
manually from the EC console.

BUG=chrome-os-partner:53336

Change-Id: I482ff52051a48441333b573f1cd0fa7f7579a6ab
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/16671
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
1 file changed