feat(sw_crc32): add software CRC32 support

Added software CRC32 support in case platform doesn't support
hardware CRC32.

Platform must include necessary Zlib source files for compilation
to use software CRC32 implementation.

Change-Id: Iecb649b2edf951944b1a7e4c250c40fe7a3bde25
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>

lib/zlib/tf_gunzip.c

 /*
- * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2021, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -9,6 +9,7 @@
 #include <string.h>
 
 #include <common/debug.h>
+#include <common/tf_crc32.h>
 #include <lib/utils.h>
 #include <tf_gunzip.h>
 
@@ -100,3 +101,15 @@ int gunzip(uintptr_t *in_buf, size_t in_len, uintptr_t *out_buf,
 
 	return ret;
 }
+
+/* Wrapper function to calculate CRC
+ * @crc: previous accumulated CRC
+ * @buf: buffer base address
+ * @size: size of the buffer
+ *
+ * Return calculated CRC32 value
+ */
+uint32_t tf_crc32(uint32_t crc, const unsigned char *buf, size_t size)
+{
+	return (uint32_t)crc32((unsigned long)crc, buf, size);
+}