xpdf: depends on freetype, so select it in kconfig as well

package/xpdf/Config.in

@@ -1,6 +1,7 @@
 config BR2_PACKAGE_XPDF
 	bool "xpdf"
 	select BR2_PACKAGE_OPENMOTIF
+	select BR2_PACKAGE_FREETYPE
 	help
 	  Xpdf is an open source viewer for Portable Document Format
 	  (PDF) files.