[SCSI] aic94xx: world-writable sysfs update_bios file

Don't allow everybody to load firmware.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Bottomley <jbottomley@parallels.com>