gator: Add config for building the module in-tree

Signed-off-by: Jon Medhurst <tixy@linaro.org>
diff --git a/drivers/Makefile b/drivers/Makefile
index 130abc1..092a62e 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -152,3 +152,5 @@
 obj-$(CONFIG_VME_BUS)		+= vme/
 obj-$(CONFIG_IPACK_BUS)		+= ipack/
 obj-$(CONFIG_NTB)		+= ntb/
+
+obj-$(CONFIG_GATOR)		+= gator/