MIPS: microMIPS: Add configuration option for microMIPS kernel.

This adds the option to build the Linux kernel using only the
microMIPS ISA. The resulting kernel binary is, at a minimum,
20% smaller than using the MIPS32R2 ISA.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>

arch/mips/kernel/proc.c

@@ -99,6 +99,10 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 	if (cpu_has_vz)		seq_printf(m, "%s", " vz");
 	seq_printf(m, "\n");
 
+	if (cpu_has_mmips) {
+		seq_printf(m, "micromips kernel\t: %s\n",
+		      (read_c0_config3() & MIPS_CONF3_ISA_OE) ?  "yes" : "no");
+	}
 	seq_printf(m, "shadow register sets\t: %d\n",
 		      cpu_data[n].srsets);
 	seq_printf(m, "kscratch registers\t: %d\n",