Merge changes from topic "marvell-a3k-makefile" into integration

Merge changes from topic "marvell-a3k-makefile" into integration

* changes:
  plat: marvell: armada: a3k: Simplify check if WTP variable is defined
  plat: marvell: armada: a3k: Split building $(WTMI_MULTI_IMG) and $(TIMDDRTOOL)
  plat: marvell: armada: Maximal size of bl1 image in mrvl_bootimage is 128kB
  plat: marvell: armada: Add missing FORCE, .PHONY and clean targets
  plat: marvell: armada: a3k: Use make ifeq/endif syntax for $(MARVELL_SECURE_BOOT) code
  plat: marvell: armada: a3k: Build $(WTMI_ENC_IMG) in $(BUILD_PLAT) directory
  plat: marvell: armada: a3k: Do not remove external WTMI image files outside of TF-A repository
  plat: marvell: armada: a3k: Do not modify $(WTMI_MULTI_IMG)
  plat: marvell: armada: a3k: Do not modify $(WTMI_IMG)