scsi: megaraid_sas: remove set but not used variable 'cur_state'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/scsi/megaraid/megaraid_sas_base.c: In function megasas_transition_to_ready:
drivers/scsi/megaraid/megaraid_sas_base.c:3900:6: warning: variable cur_state set but not used [-Wunused-but-set-variable]

Never used since commit 7218df69 ("[SCSI] megaraid_sas: use the
firmware boot timeout when waiting for commands")

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