sh: Restrict old CMT timer code to SH-2/SH-2A.

None of the other platforms use this, and need individual porting.
Restrict it back to the supported set of CPU subtypes.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/Kconfig

@@ -419,7 +419,7 @@ config SH_TMU
 
 config SH_CMT
 	bool "CMT timer support"
-	depends on SYS_SUPPORTS_CMT
+	depends on SYS_SUPPORTS_CMT && CPU_SH2
 	default y
 	help
 	  This enables the use of the CMT as the system timer.