sh: Fix up SH-3 and SH-4 driver dependencies.

Both shwdt and rtc-sh are only supported on SH-3 and SH-4 at
the moment, don't allow them to break the SH-2 and SH-5 (sh64)
builds.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index cea401f..35f3466 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -394,7 +394,7 @@
 
 config RTC_DRV_SH
 	tristate "SuperH On-Chip RTC"
-	depends on RTC_CLASS && SUPERH
+	depends on RTC_CLASS && SUPERH && (CPU_SH3 || CPU_SH4)
 	help
 	  Say Y here to enable support for the on-chip RTC found in
 	  most SuperH processors.