Add base-passwd to swupdate image

This removes some warnings at start up because
/etc/passwd cannot be parsed:

chown: unknown user/group root:root

Signed-off-by: Stefano Babic <sbabic@denx.de>

recipes-extended/images/swupdate-image.bb

@@ -9,6 +9,7 @@ DESCRIPTION = "Root FS includes the following functionality: 				\
 		"
 
 IMAGE_INSTALL = "base-files \
+		base-passwd \
 		busybox \
 		mtd-utils \
 		mtd-utils-ubifs \