libc: Fix some MISRA defects ...

No functional changes.

Change-Id: I907aa47565af2a6c435a5560041fd2b59e65c25c
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

libc: Move tf_printf and tf_snprintf to libc ...

Change their names to printf and snprintf. They are much smaller than
the previous versions we had, which makes them better suited for the
Trusted Firmware.

Change-Id: Ia872af91b7b967c47fce012eccecede7873a3daf
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>