scsi: mpt3sas: Remove NULL check before freeing function

Fix the following coccicheck warning:

drivers/scsi/mpt3sas/mpt3sas_base.c:4906:3-19: WARNING: NULL check
before some freeing functions is not needed.

Link: https://lore.kernel.org/r/20200418095850.34883-1-yanaijie@huawei.com


Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>