zlib: add gunzip() support

This commit adds some more files to use zlib from TF.

To use zlib, ->zalloc and ->zfree hooks are needed.  The implementation
depends on the system.  For user-space, the libc provides malloc() and
friends.  Unfortunately, ARM Trusted Firmware does not provide malloc()
or any concept of dynamic memory allocation.

I implemented very simple calloc() and free() for this.  Stupidly,
zfree() never frees memory, but it works enough for this.

The purpose of using zlib is to implement gunzip() - this function
takes compressed data from in_buf, then dumps the decompressed data
to oub_buf.  The work_buf is used for memory allocation during the
decompress.  Upon exit, it updates in_buf and out_buf.  If successful,
in_buf points to the end of input data, out_buf to the end of the
decompressed data.

To use this feature, you need to do:

 - include lib/zlib/zlib.mk from your platform.mk

 - add $(ZLIB_SOURCES) to your BL*_SOURCES

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/include/lib/zlib/tf_gunzip.h b/include/lib/zlib/tf_gunzip.h
new file mode 100644
index 0000000..46d20eb
--- /dev/null
+++ b/include/lib/zlib/tf_gunzip.h
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __TF_GUNZIP_H__
+#define __TF_GUNZIP_H__
+
+#include <stddef.h>
+#include <stdint.h>
+
+int gunzip(uintptr_t *in_buf, size_t in_len, uintptr_t *out_buf,
+	   size_t out_len, uintptr_t work_buf, size_t work_len);
+
+#endif /* __TF_GUNZIP_H___ */