Current binary wtptp/linux/tbb_linux which is specified in $(DOIMAGETOOL)
variable points to external pre-compiled Marvell x86_64 ELF linux binary
from A3700-utils-marvell WTP repository.

It means that currently it is not possible to compile TF-A for A3720 on
other host platform then linux x86_64.

Part of the A3700-utils-marvell WTP repository is also source code of
$(DOIMAGETOOL) TBB_Linux tool.

This change adds support for building $(DOIMAGETOOL) also for a3k platform.

After running $(MAKE) at appropriate subdirectory of A3700-utils-marvell
WTP repository, compiled TBB_linux tool will appear in WTP subdirectory
wtptp/src/TBB_Linux/release/. So update also $(DOIMAGETOOL) variable to
point to the correct location where TBB_linux was built.

To build TBB_linux it is required to compile external Crypto++ library
which is available at: https://github.com/weidai11/cryptopp.git



User needs to set CRYPTOPP_PATH option to specify path to that library.

After this change it is now possible to build whole firmware for A3720
platform without requirement to use pre-compiled/proprietary x86_64
executable binaries from Marvell.

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I6f26bd4356778a2f8f730a223067a2e550e6c8e0