image_decompress: add APIs for decompressing images

These APIs are used by platforms that need to decompress images.

image_decompress_init():
  This registers a temporary buffer and a decompressor callback.
  This should be called from platform init code.

image_decompress_prepare():
  This should be called before each compressed image is loaded.  The
  best location to call this will be bl*_plat_handle_pre_image_load().

image_decompress():
  This should be called after each compressed image is loaded.  The
  best location to call this will be bl*_plat_handle_post_image_load().

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/include/common/image_decompress.h b/include/common/image_decompress.h
new file mode 100644
index 0000000..aed8df3
--- /dev/null
+++ b/include/common/image_decompress.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __IMAGE_DECOMPRESS_H__
+#define __IMAGE_DECOMPRESS_H__
+
+#include <stddef.h>
+#include <stdint.h>
+
+struct image_info;
+
+typedef int (decompressor_t)(uintptr_t *in_buf, size_t in_len,
+			     uintptr_t *out_buf, size_t out_len,
+			     uintptr_t work_buf, size_t work_len);
+
+void image_decompress_init(uintptr_t buf_base, uint32_t buf_size,
+			   decompressor_t *decompressor);
+void image_decompress_prepare(struct image_info *info);
+int image_decompress(struct image_info *info);
+
+#endif /* __IMAGE_DECOMPRESS_H___ */