sh: Use sh7203 GPIO on rsk7203 board

Make the rsk7203 board use the newly added sh7203 pinmux code.
Only a single LED plus the serial console pins for now.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/boards/Kconfig b/arch/sh/boards/Kconfig
index 2a05919..6c4cbf1 100644
--- a/arch/sh/boards/Kconfig
+++ b/arch/sh/boards/Kconfig
@@ -128,6 +128,7 @@
 
 config SH_RSK7203
 	bool "RSK7203"
+	select GENERIC_GPIO
 	depends on CPU_SUBTYPE_SH7203
 
 config SH_SDK7780