[SCSI] scsi_error.c: Export some scsi_eh_* functions

Export a couple of functions from scsi_error that are needed to handle
failed SCSI commands from the SAS EH.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>

make exports GPL and
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>