scsi: megaraid: Remove redundant code in megasas_alloc_cmds

megasas_alloc_cmds is to alloc cmd_list of instance instead of fusion,
and fusion is useless in this function. Just remove it.

Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>