sh: remove support for sh7300 and solution engine 7300

This patch removes old dead code:
- kill off sh7300 cpu support
- get rid of broken solution engine 7300 board support

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/mm/Kconfig

@@ -63,10 +63,6 @@ config CPU_SUBTYPE_SH7206
 
 # SH-3 Processor Support
 
-config CPU_SUBTYPE_SH7300
-	bool "Support SH7300 processor"
-	select CPU_SH3
-
 config CPU_SUBTYPE_SH7705
 	bool "Support SH7705 processor"
 	select CPU_SH3