[ARM] Add linux/errno.h include to allow pcf8583.c to build.

drivers/acorn/char/pcf8583.c

@@ -14,6 +14,7 @@
 #include <linux/string.h>
 #include <linux/mc146818rtc.h>
 #include <linux/init.h>
+#include <linux/errno.h>
 #include <linux/bcd.h>
 
 #include "pcf8583.h"