scsi: megaraid_sas: fix spelling mistake "megarid_sas" -> "megaraid_sas"

Fix spelling mistake in kernel warning message and replace printk with with
pr_warn.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>