[SCSI] gdth: kill gdth_{read,write}[bwl] wrappers

They are direct equivalents to {read,write}[bwl].
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>