MIPS: Fix clean of vmlinuz.{32,ecoff,bin,srec}

Make doesn't expand shell style "vmlinuz.{32,ecoff,bin,srec}" to the 4
separate files, so none of these files get cleaned up by make clean.
List the files separately instead.

Fixes: ec3352925b74 ("MIPS: Remove all generated vmlinuz* files on "make clean"")
Signed-off-by: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/18491/

arch/mips/boot/compressed/Makefile

@@ -133,4 +133,8 @@ vmlinuz.srec: vmlinuz
 uzImage.bin: vmlinuz.bin FORCE
 	$(call if_changed,uimage,none)
 
-clean-files := $(objtree)/vmlinuz $(objtree)/vmlinuz.{32,ecoff,bin,srec}
+clean-files += $(objtree)/vmlinuz
+clean-files += $(objtree)/vmlinuz.32
+clean-files += $(objtree)/vmlinuz.ecoff
+clean-files += $(objtree)/vmlinuz.bin
+clean-files += $(objtree)/vmlinuz.srec