fix: increase TSRAM to 384KB for fvp-tbb-mbedtls-no-cohmem build

This helps to resolve the following build fail:

aarch64-none-elf-ld.bfd: BL31 progbits has exceeded its limit. Consider disabling some features.
make: *** [Makefile:1497: /home/buildslave/workspace/tf-a-builder/trusted-firmware-a/build/fvp/debug/bl31/bl31.elf] Error 1

Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: I0b40109bf97ca9b7877fce22583ddd0e3afccd53
1 file changed