sh: Add RSK2+SH7264 board

The RSK2+SH7264 board uses the sh7264 processor. It is often
referred to as just rsk7264. NOR Flash, SDRAM, serial, USB Host and
ethernet are working.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/boards/Kconfig

@@ -133,7 +133,7 @@ config SH_RTS7751R2D
 
 config SH_RSK
 	bool "Renesas Starter Kit"
-	depends on CPU_SUBTYPE_SH7201 || CPU_SUBTYPE_SH7203
+	depends on CPU_SUBTYPE_SH7201 || CPU_SUBTYPE_SH7203 || CPU_SUBTYPE_SH7264
 	help
 	 Select this option if configuring for any of the RSK+ MCU
 	 evaluation platforms.