sh: rsk7203: Move to boards.cfg

Move the rsk7203 target out of the Makefile and into boards.cfg.
And fix sh2 of MAKEALL.

Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/MAKEALL b/MAKEALL
index 51312dd..a97061c 100755
--- a/MAKEALL
+++ b/MAKEALL
@@ -609,9 +609,8 @@
 ## SH Systems
 #########################################################################
 
-LIST_sh2="		\
-	rsk7203		\
-"
+LIST_sh2="$(boards_by_cpu sh2)"
+
 LIST_sh3="		\
 	mpr2		\
 	ms7720se	\