megaraid_sas: add missing curly braces in ioctl handler

gcc-6 found a dubious indentation in the megasas_mgmt_fw_ioctl
function:

drivers/scsi/megaraid/megaraid_sas_base.c: In function 'megasas_mgmt_fw_ioctl':
drivers/scsi/megaraid/megaraid_sas_base.c:6658:4: warning: statement is indented as if it were guarded by... [-Wmisleading-indentation]
    kbuff_arr[i] = NULL;
    ^~~~~~~~~
drivers/scsi/megaraid/megaraid_sas_base.c:6653:3: note: ...this 'if' clause, but it is not
   if (kbuff_arr[i])
   ^~

The code is actually correct, as there is no downside in clearing a NULL
pointer again.

This clarifies the code and avoids the warning by adding extra curly
braces.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 90dc9d98 ("megaraid_sas : MFI MPT linked list corruption fix")
Reviewed-by: Hannes Reinecke <hare@suse.com>
Acked-by: Sumit Saxena <sumit.saxena@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>