squashfs: fix zlib dependency

The 'gzip' compression supports just needs zlib, and not the gzip package.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/squashfs/Config.in

@@ -11,7 +11,7 @@ if BR2_PACKAGE_SQUASHFS
 config BR2_PACKAGE_SQUASHFS_GZIP
        bool "gzip support"
        default y
-       select BR2_PACKAGE_GZIP
+       select BR2_PACKAGE_ZLIB
        help
          Support GZIP compression algorithm