drivers: add GIC support

The GIC is ARM's "Generic Interrupt Controller". This
change essentially implements the rudimentary support
for a GICv2 implementation that routes all interrupts
to Group1. This should also work for GICv1 with security
extensions.

BUG=chrome-os-partner:31945
BRANCH=None
TEST=Built and booted kernel using the code.

Change-Id: I9c9202c1309ca9e711e00d742085a6728552c54b
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: d1cd9b6b76035af107b7dc876f90777698162d34
Original-Change-Id: I4c5b84bfe888ac33fa01c8d64a3dffe1b5ddc823
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/217512
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9075
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <edward.ocallaghan@koparo.com>
diff --git a/src/drivers/gic/Makefile.inc b/src/drivers/gic/Makefile.inc
new file mode 100644
index 0000000..51e3e19
--- /dev/null
+++ b/src/drivers/gic/Makefile.inc
@@ -0,0 +1 @@
+ramstage-$(CONFIG_GIC) += gic.c