MIPS: Remove all generated vmlinuz* files on "make clean"

[Ralf: I changed the patch to explicitly list all files to be deleted out
of paranoia.]
Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/1590/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/boot/compressed/Makefile

@@ -105,4 +105,4 @@ OBJCOPYFLAGS_vmlinuz.srec := $(OBJCOPYFLAGS) -S -O srec
 vmlinuz.srec: vmlinuz
 	$(call cmd,objcopy)
 
-clean-files := $(objtree)/vmlinuz.*
+clean-files := $(objtree)/vmlinuz $(objtree)/vmlinuz.{32,ecoff,bin,srec}