scsi: mptconfig: fix an assert expression

When LSI SAS1068 Host Bus emulator builds configuration page
headers, mptsas_config_pack() should assert that the size
fits in a byte.  However, the size is expressed in 32-bit
units, so up to 1020 bytes fit.  The assertion was only
allowing replies up to 252 bytes, so fix it.
Suggested-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPrasad J Pandit <pjp@fedoraproject.org>
Message-Id: <1472645167-30765-2-git-send-email-ppandit@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/scsi/mptconfig.c

@@ -158,7 +158,7 @@ static size_t mptsas_config_pack(uint8_t **data, const char *fmt, ...)
     va_end(ap);
 
     if (data) {
-        assert(ret < 256 && (ret % 4) == 0);
+        assert(ret / 4 < 256 && (ret % 4) == 0);
         stb_p(*data + 1, ret / 4);
     }
     return ret;