scsi: ufs: core: Pass EHS length into ufshcd_prepare_req_desc_hdr()

We need to fill in the total EHS length in UTP Transfer Request Descriptor.
Add this functionality to ufshcd_prepare_req_desc_hdr().

Signed-off-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>