spl: lz4: Allow use of lz4 compression in SPL

In some cases U-Boot is compressed and it is useful to be able to
decompress it in SPL. Add a Kconfig and Makefile change to allow this.
Note that this does not actually implement decompression.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/Kconfig b/lib/Kconfig
index 847e797..0333ab1 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -301,6 +301,14 @@
 	help
 	  This enables support for LZO compression algorithm.r
 
+config SPL_LZ4
+	bool "Enable LZ4 decompression support in SPL"
+	help
+	  This enables support for tge LZ4 decompression algorithm in SPL. LZ4
+	  is a lossless data compression algorithm that is focused on
+	  fast compression and decompression speed. It belongs to the LZ77
+	  family of byte-oriented compression schemes.
+
 config SPL_LZO
 	bool "Enable LZO decompression support in SPL"
 	help