scsi: megasas: null terminate bios version buffer

While reading information via 'megasas_ctrl_get_info' routine,
a local bios version buffer isn't null terminated. Add the
terminating null byte to avoid any OOB access.

Reported-by: Li Qiang <liqiang6-s@360.cn>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/scsi/megasas.c

@@ -773,6 +773,7 @@ static int megasas_ctrl_get_info(MegasasState *s, MegasasCmd *cmd)
 
         ptr = memory_region_get_ram_ptr(&pci_dev->rom);
         memcpy(biosver, ptr + 0x41, 31);
+        biosver[31] = 0;
         memcpy(info.image_component[1].name, "BIOS", 4);
         memcpy(info.image_component[1].version, biosver,
                strlen((const char *)biosver));