vof: add distclean target

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[AJB: add clean dep to distclean]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220929114231.583801-16-alex.bennee@linaro.org>

pc-bios/vof/Makefile

@@ -19,4 +19,6 @@ vof.elf: entry.o main.o ci.o bootmem.o libc.o
 clean:
 	rm -f *.o vof.bin vof.elf *~
 
-.PHONY: all clean
+distclean: clean
+
+.PHONY: all clean distclean