greybus: makefile: fix unused cflags

The ccflags variable was spelled wrong, so no extra compilation flags
could be specified.

The proper flag is 'ccflags-y.'
Signed-off-by: Perry Hung <perry@leaflabs.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/Makefile

@@ -66,7 +66,7 @@ $(foreach opt,$(CONFIG_OPTIONS_DISABLE),$(if $(filter m y, $(CONFIG_$(opt))), \
 endif
 
 # add -Wall to try to catch everything we can.
-ccFlags-y := -Wall
+ccflags-y := -Wall
 
 all: module