swupdate: add xz dependency for CONFIG_XZ

Add xz to DEPENDS so builds with CONFIG_XZ=y have the required headers and library available.

Signed-off-by: He Yong <hyyoxhk@163.com>

recipes-support/swupdate/swupdate.inc

@@ -198,6 +198,9 @@ python () {
     if 'CONFIG_ZSTD=y\n' in features:
         depends += ' zstd'
 
+    if 'CONFIG_XZ=y\n' in features:
+        depends += ' xz'
+
     if 'CONFIG_DISKPART=y\n' in features:
         depends += ' util-linux e2fsprogs'