If MCQ support is present, enabling it after MCQ support has been
configured would require reallocating tags and memory.  It would also free
up the already allocated memory in Single Doorbell Mode. So defer invoking
scsi_add_host() until MCQ is configured.

Co-developed-by: Can Guo <quic_cang@quicinc.com>
Signed-off-by: Can Guo <quic_cang@quicinc.com>
Signed-off-by: Asutosh Das <quic_asutoshd@quicinc.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>