kbuild: Accept various mips sub-types in SUBARCH

uname -m on MIPS can give a number of results, such as mips64.  We
need to add another substitution to the sed call for SUBARCH in the
main Makefile.
Signed-off-by: NMartin Michlmayr <tbm@cyrius.com>
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

Makefile

@@ -151,7 +151,7 @@ export srctree objtree VPATH TOPDIR
 SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ \
 				  -e s/arm.*/arm/ -e s/sa110/arm/ \
 				  -e s/s390x/s390/ -e s/parisc64/parisc/ \
-				  -e s/ppc.*/powerpc/ )
+				  -e s/ppc.*/powerpc/ -e s/mips.*/mips/ )
 
 # Cross compiling and selecting different set of gcc/bin-utils
 # ---------------------------------------------------------------------------