[SCSI] wd33c93: Kill empty wd33c93_release()

wd33c93_release() has been empty since ages, and sgiwd93.c no longer calls it
since its conversion to a proper platform driver 2 years ago. Also remove the
callers in the m68k wd33c93 shims.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>