lib: Add a Kconfig for SPL_BZIP2

This is implicitly used in the source and seems useful, so add it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/Kconfig b/lib/Kconfig
index 83e5edd..1c93f52 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -727,6 +727,12 @@
 
 endif
 
+config SPL_BZIP2
+	bool "Enable bzip2 decompression support for SPL build"
+	depends on SPL
+	help
+	  This enables support for bzip2 compression algorithm for SPL boot.
+
 config SPL_LZ4
 	bool "Enable LZ4 decompression support in SPL"
 	depends on SPL