plat: marvell: armada: Add missing FORCE, .PHONY and clean targets

FORCE target is used as a dependency for other file targets which needs to
be always rebuilt. .PHONY target is standard Makefile target which specify
non-file targets and therefore needs to be always rebuilt.

Targets clean, realclean and distclean are .PHONY targets used to remove
built files. Correctly set that mrvl_clean target is prerequisite for these
clean targets to ensure that built files are removed.

Finally this change with usage of FORCE target allows to remove mrvl_clean
hack from the prerequisites of a8k ${DOIMAGETOOL} target which was used
just to ensure that ${DOIMAGETOOL} is always rebuilt via make subprocess.

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I2fa8971244b43f101d846fc433ef7b0b6f139c92
diff --git a/plat/marvell/armada/a8k/common/a8k_common.mk b/plat/marvell/armada/a8k/common/a8k_common.mk
index 58394a4..cf1516a 100644
--- a/plat/marvell/armada/a8k/common/a8k_common.mk
+++ b/plat/marvell/armada/a8k/common/a8k_common.mk
@@ -152,14 +152,20 @@
 include ${BLE_PATH}/ble.mk
 $(eval $(call MAKE_BL,e))
 
+clean realclean distclean: mrvl_clean
+
+.PHONY: mrvl_clean
 mrvl_clean:
 	@echo "  Doimage CLEAN"
 	${Q}${MAKE} PLAT=${PLAT} --no-print-directory -C ${DOIMAGEPATH} clean
 
-${DOIMAGETOOL}: mrvl_clean
+${DOIMAGETOOL}: FORCE
 	@$(DOIMAGE_LIBS_CHECK)
 	${Q}${MAKE} --no-print-directory -C ${DOIMAGEPATH}
 
+.PHONY: mrvl_flash
 mrvl_flash: ${BUILD_PLAT}/${BOOT_IMAGE} ${DOIMAGETOOL}
 	${DOIMAGETOOL} ${DOIMAGE_FLAGS} ${BUILD_PLAT}/${BOOT_IMAGE} ${BUILD_PLAT}/${FLASH_IMAGE}
 
+.PHONY: FORCE
+FORCE:;