Blackfin: stop cleaning include/asm/asm-offsets.h

The file is no longer generated, so we don't want to clean it.

Reported-by: Vivi Li <vivi.li@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/Makefile b/arch/blackfin/Makefile
index ba84206..5a97a31 100644
--- a/arch/blackfin/Makefile
+++ b/arch/blackfin/Makefile
@@ -133,7 +133,6 @@
 KBUILD_CPPFLAGS	+= $(patsubst %,-I$(srctree)/%include,$(machdirs))
 
 CLEAN_FILES += \
-	arch/$(ARCH)/include/asm/asm-offsets.h \
 	arch/$(ARCH)/kernel/asm-offsets.s \
 
 archclean: