TFTF: Add missing D-cache invalidation

This patch adds missing D-cache invalidation of RW memory
in tftf_entrypoint to safeguard against possible corruption
of this memory by dirty cache lines in a system cache as
a result of use by an earlier boot loader stage.
Ref. GENFW-3455

Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Change-Id: I595344c307502a6c24c2e62d3e3f2f9d7a810dfa
2 files changed