[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/Kconfig b/arch/mips/Kconfig
index 77e3d24..2e4ac65 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -82,6 +82,7 @@
 	bool "DECstations"
 	select BOOT_ELF32
 	select CEVT_R4K
+	select CSRC_IOASIC
 	select CSRC_R4K
 	select CPU_DADDI_WORKAROUNDS if 64BIT
 	select CPU_R4000_WORKAROUNDS if 64BIT
@@ -784,6 +785,9 @@
 config CSRC_BCM1480
 	bool
 
+config CSRC_IOASIC
+	bool
+
 config CSRC_R4K
 	bool