MIPS: ARC: Fix build of firmware library on uniprocessor.

Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/include/asm/smp-ops.h

···
 #ifndef __ASM_SMP_OPS_H
 #define __ASM_SMP_OPS_H
 
+#include <linux/errno.h>
+
 #ifdef CONFIG_SMP
 
 #include <linux/cpumask.h>