m68knommu: fix make archclean

Remove build reference to arch/m68knommu/boot directory, it doesn't
exist.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/m68knommu/Makefile b/arch/m68knommu/Makefile
index 1235f80..30aa255 100644
--- a/arch/m68knommu/Makefile
+++ b/arch/m68knommu/Makefile
@@ -118,4 +118,4 @@
 libs-y	+= arch/m68knommu/lib/
 
 archclean:
-	$(Q)$(MAKE) $(clean)=arch/m68knommu/boot
+