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>
diff --git a/lib/libc/printf.c b/lib/libc/printf.c
index a1a8024..4f4a722 100644
--- a/lib/libc/printf.c
+++ b/lib/libc/printf.c
@@ -9,7 +9,7 @@
 #include <stdint.h>
 
 /***********************************************************
- * The tf_printf implementation for all BL stages
+ * The printf implementation for all BL stages
  ***********************************************************/
 
 #define get_num_va_args(_args, _lcount) \