[MIPS] ARC: Get rid of mips_machgroup

This has not been any serious user of this ill conceived thing since the
original invention in like '95.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/cobalt/setup.c

@@ -114,8 +114,6 @@ void __init prom_init(void)
 	unsigned long memsz;
 	char **argv;
 
-	mips_machgroup = MACH_GROUP_COBALT;
-
 	memsz = fw_arg0 & 0x7fff0000;
 	narg = fw_arg0 & 0x0000ffff;