xmlpool: remove the clean target

... by folding it into CLEANFILES. Don't worry about $(LANG) as it is
essentially the first folder of $(POS). With the latter already handled.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/mesa/drivers/dri/common/xmlpool/Makefile.am

@@ -61,12 +61,10 @@ EXTRA_DIST = \
 	SConscript
 
 BUILT_SOURCES = options.h
-CLEANFILES = $(MOS) options.h
-
-# All generated files are cleaned up.
-clean:
-	-rm -f $(POT) options.h *~
-	-rm -rf $(LANGS)
+CLEANFILES = \
+	options.h
+	$(POS) \
+	$(MOS)
 
 # Default target options.h
 options.h: LOCALEDIR := .