libc: Use printf and snprintf across codebase

tf_printf and tf_snprintf are now called printf and snprintf, so the
code needs to be updated.

Change-Id: Iffeee97afcd6328c4c2d30830d4923b964682d71
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
18 files changed