[MIPS] add DECstation I/O ASIC clocksource

Add DECstation I/O ASIC clocksource

Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/dec/time.c b/arch/mips/dec/time.c
index 603490625..0cbab8d 100644
--- a/arch/mips/dec/time.c
+++ b/arch/mips/dec/time.c
@@ -165,7 +165,7 @@
 
 	if (!cpu_has_counter && IOASIC)
 		/* For pre-R4k systems we use the I/O ASIC's counter.  */
-		clocksource_mips.read = dec_ioasic_hpt_read;
+		dec_ioasic_clocksource_init();
 
 	/* Set up the rate of periodic DS1287 interrupts.  */
 	CMOS_WRITE(RTC_REF_CLCK_32KHZ | (16 - __ffs(HZ)), RTC_REG_A);