nvme-fabrics: ignore invalid fast_io_fail_tmo values

Valid fast_io_fail_tmo values are integers >= 0 or -1 (disabled).
Prevent userspace from setting arbitrary negative values.

Signed-off-by: Maurizio Lombardi <[e-mail]>
Reviewed-by: Sagi Grimberg <[e-mail]>
Reviewed-by: Chaitanya Kulkarni <[e-mail]>
Signed-off-by: Christoph Hellwig <[e-mail]>

drivers/nvme/host/fabrics.c

···
 			if (token >= 0)
 				pr_warn("I/O fail on reconnect controller after %d sec\n",
 					token);
+			else
+				token = -1;
+
 			opts->fast_io_fail_tmo = token;
 			break;
 		case NVMF_OPT_HOSTNQN: