scsi: be2iscsi: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the actual
output size, the succeeding calls may go beyond the given buffer limit.
Fix it by replacing with scnprintf().

Link: https://lore.kernel.org/r/20200315094241.9086-3-tiwai@suse.de


Cc: "James E . J . Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>
Cc: Subbu Seetharaman <subbu.seetharaman@broadcom.com>
Cc: Ketan Mukadam <ketan.mukadam@broadcom.com>
Cc: Jitendra Bhivare <jitendra.bhivare@broadcom.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>