Introduce LINUX_COMMON_TARGETS

For all concerned platforms, move the targets currently assigned to
LINUX_COMMON_FLAGS into the new LINUX_COMMON_TARGETS variable and use
that in the "linux-common:" target.

This makes the LINUX_CLEAN_COMMON_FLAGS and LINUX_CLEANER_COMMON_FLAGS
redundant so they are replaced by LINUX_COMMON_FLAGS.

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@foss.st.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
diff --git a/hikey960.mk b/hikey960.mk
index 9fc8ba2..18cf8df 100644
--- a/hikey960.mk
+++ b/hikey960.mk
@@ -169,7 +169,8 @@
 		LOCALVERSION= \
 		gen_init_cpio
 
-LINUX_COMMON_FLAGS += ARCH=arm64 Image hisilicon/hi3660-hikey960.dtb
+LINUX_COMMON_FLAGS += ARCH=arm64
+LINUX_COMMON_TARGETS += Image hisilicon/hi3660-hikey960.dtb
 
 .PHONY: linux
 linux: linux-common