Include file plat/marvell/marvell.mk for platform A3700 was included two
times. Once from file plat/marvell/armada/a3k/common/a3700_common.mk and
second time from common file plat/marvell/armada/common/marvell_common.mk.

It caused following warning every time was make called:

    plat/marvell/marvell.mk:51: warning: overriding recipe for target 'mrvl_clean'
    plat/marvell/marvell.mk:51: warning: ignoring old recipe for target 'mrvl_clean'

Change in this commit removes inclusion of plat/marvell/marvell.mk file in
common file plat/marvell/armada/common/marvell_common.mk. As a80x0 platform
needs this include file, add it also into a80x0 platform specific include
file lat/marvell/armada/a8k/common/a8k_common.mk.

Also moves inclusion of plat/marvell/marvell.mk file in a3700 platform file
plat/marvell/armada/a3k/common/a3700_common.mk at correct place. Global
plat/marvell/marvell.mk expects that variables DOIMAGEPATH and DOIMAGETOOL
are already defined, but it defines MARVELL_SECURE_BOOT variable which is
needed by plat/marvell/armada/a3k/common/a3700_common.mk.

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I5cbbd7eb8a3376924419f9850516b2a4924be5aa