x86: teach vdso to clean

A few files remained after 'make clean' in arch/x86/vdso/.
Teach vdso to clean up those files in a bit brutal fashion.
The filenames are just hardcoded in the Makefile.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Roland McGrath <roland@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/vdso/Makefile

@@ -130,3 +130,5 @@ $(vdso-install-y): %.so: $(obj)/%.so.dbg FORCE
 
 PHONY += vdso_install $(vdso-install-y)
 vdso_install: $(vdso-install-y)
+
+clean-files := vdso32-syscall* vdso32-sysenter* vdso32-int80*