Introduce tf_vprintf() and tf_string_print()

This patch introduces tf_vprintf() and tf_string_print() APIs
which is needed by the logging framework introduced in a later
patch.

Change-Id: Ie4240443d0e04e070502b51e371e546dd469fd33
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
2 files changed