libc: Import strtol from FreeBSD project

From commit: 21571b1d140ae7bb44e94c0afba2ec61456b275b
The coding guidelines[1] in TF-A forbid the use of ato*() functions
in favour of strto*(). However, the TF-A libc does not provide an
implementation of strto*(), making this rule impossible to satisfy.

Also made small changes to fit into TF-A project. Added the source
files to the libc makefile

[1] https://trustedfirmware-a.readthedocs.io/en/latest/process/coding-guidelines.html#libc-functions-that-are-banned-or-to-be-used-with-caution

Change-Id: Ica95bf5da722913834fe90bf3fe743aa34e01e80
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/lib/libc/libc_asm.mk b/lib/libc/libc_asm.mk
index 6416a3c..1597da4 100644
--- a/lib/libc/libc_asm.mk
+++ b/lib/libc/libc_asm.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2020, Arm Limited. All rights reserved.
+# Copyright (c) 2020-2021, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -19,11 +19,14 @@
 			snprintf.c			\
 			strchr.c			\
 			strcmp.c			\
+			strlcat.c			\
 			strlcpy.c			\
 			strlen.c			\
 			strncmp.c			\
 			strnlen.c			\
-			strrchr.c)
+			strrchr.c			\
+			strtok.c			\
+			strtol.c)
 
 ifeq (${ARCH},aarch64)
 LIBC_SRCS	+=	$(addprefix lib/libc/aarch64/,	\