MIPS: ath25: add common parts

Add common code for Atheros AR5312 and Atheros AR2315 SoCs families.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Cc: Linux MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/8237
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/ath25/devices.h

@@ -0,0 +1,18 @@
+#ifndef __ATH25_DEVICES_H
+#define __ATH25_DEVICES_H
+
+#include <linux/cpu.h>
+
+#define ATH25_REG_MS(_val, _field)	(((_val) & _field##_M) >> _field##_S)
+
+static inline bool is_ar2315(void)
+{
+	return (current_cpu_data.cputype == CPU_4KEC);
+}
+
+static inline bool is_ar5312(void)
+{
+	return !is_ar2315();
+}
+
+#endif