For building fip image it is not needed to build target mrvl_flash. This
fip image contains only bl2, bl31 and bl33 (u-boot.bin) images and
therefore it does not depend on Marvell wtmi and wtp A3700-utils.

So remove mrvl_flash dependency for fip target to allow building fip image
without need to build mrvl_flash and therefore specify and provide Marvell
wmi and wtp A3700-utils.

This changes fixes compilation of fip image for A3700 platform by command:

    make CROSS_COMPILE=aarch64-linux-gnu- BL33=/path/u-boot/u-boot.bin \
         DEBUG=0 LOG_LEVEL=0 USE_COHERENT_MEM=0 PLAT=a3700 fip

Marvell boot image can be still build by 'mrvl_flash' target.

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: Iba9a9da5be6fd1da23407fc2d490aedcb1a292c9