Replace 'all-clean' targets with 'clean'

Signed-off-by: Victor Chong <victor.chong@linaro.org>
Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
diff --git a/fvp.mk b/fvp.mk
index 3535b12..9cfd18e 100644
--- a/fvp.mk
+++ b/fvp.mk
@@ -28,7 +28,7 @@
 # Targets
 ################################################################################
 all: arm-tf edk2 linux optee-os optee-client xtest helloworld
-all-clean: arm-tf-clean busybox-clean edk2-clean optee-os-clean \
+clean: arm-tf-clean busybox-clean edk2-clean optee-os-clean \
 	optee-client-clean