Makefile: Remove tags file on mrproper

make tags creates a symbolic link called tags to ctags. Remove this file
on make mrproper or make distclean.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

Makefile

@@ -1427,7 +1427,7 @@ CLEAN_FILES += include/bmp_logo.h include/bmp_logo_data.h include/license.h \
 MRPROPER_DIRS  += include/config include/generated spl tpl \
 		  .tmp_objdiff
 MRPROPER_FILES += .config .config.old include/autoconf.mk* include/config.h \
-		  ctags etags TAGS cscope* GPATH GTAGS GRTAGS GSYMS
+		  ctags etags tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS
 
 # clean - Delete most, but leave enough to build external modules
 #