openpower/libflash: Use SKIBOOT_VERSION

libflash code sits inside skiboot source tree. Use SKIBOOT_VERSION
instead of having separate version.

Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
diff --git a/openpower/package/libflash/Config.in b/openpower/package/libflash/Config.in
index b4f6c7a..247bcc6 100644
--- a/openpower/package/libflash/Config.in
+++ b/openpower/package/libflash/Config.in
@@ -1,5 +1,6 @@
 config BR2_PACKAGE_LIBFLASH
 	bool "libflash"
+	depends on BR2_PACKAGE_SKIBOOT
 	help
 	  Build libflash shared library