include/u-boot, lib/zlib: add sources for zlib decompression

Add zlib (v1.2.11) uncompr() function to U-Boot. SquashFS depends on
this function to decompress data from a raw disk image. The actual
support for zlib into SquashFS sources will be added in a follow-up
commit.

Signed-off-by: Joao Marcos Costa <joaomarcos.costa@bootlin.com>
diff --git a/lib/Kconfig b/lib/Kconfig
index 2142bd0..089348a 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -460,6 +460,13 @@
 	help
 	  This enables support for GZIP compression algorithm.
 
+config ZLIB_UNCOMPRESS
+	bool "Enables zlib's uncompress() functionality"
+	help
+	  This enables an extra zlib functionality: the uncompress() function,
+	  which decompresses data from a buffer into another, knowing their
+	  sizes. Unlike gunzip(), there is no header parsing.
+
 config GZIP_COMPRESSED
 	bool
 	select ZLIB