sgm: Fix bl2 sources
sgm: Fix bl2 sources

The weak version of plat_get_mbedtls_heap() was being used.

Change-Id: I6da331a098dd1af5bb64729d5b914cfb74b8869e
Signed-off-by: Ambroise Vincent <6526170e434f61edb2744ad8311ffdc62335a3f7@arm.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware