libc: armclang: Implement compiler printf symbols

armclang replaces calls to printf by calls to one of the symbols
__0printf, __1printf or __2printf. This patch adds new functions with
these names that internally call printf so that the Trusted Firmware can
be compiled with this compiler.

Change-Id: I06a0e3e5001232fe5b2577615666ddd66e81eef0
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>