greybus: add -Wall to the build flags

In an attempt to turn on as many options as we can to catch warnings
early, let's enable -Wall.
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
Reviewed-by: Alex Elder <elder@linaro.org>

drivers/staging/greybus/Makefile

@@ -23,6 +23,9 @@ KERNELVER		?= $(shell uname -r)
 KERNELDIR 		?= /lib/modules/$(KERNELVER)/build
 PWD			:= $(shell pwd)
 
+# add -Wall to try to catch everything we can.
+ccFlags-y := -Wall
+
 all: module
 
 module: