sh: remove CPU_SUBTYPE_SH7764

The symbol is an orphan, get rid of it.

Submitted by Richard a few months ago as "[PATCH 21/28] Remove
CPU_SUBTYPE_SH7764".

[pebolle@tiscali.nl: re-added dropped ||]
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>