um: Fix uml_mconsole stop/go

Moving to an EPOLL based IRQ controller broke uml_mconsole stop/go
commands. This fixes it and restores stop/go functionality.

Fixes: ff6a1798 ("Epoll based IRQ controller")
Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/mconsole_kern.c

@@ -224,7 +224,7 @@ void mconsole_go(struct mc_request *req)
 
 void mconsole_stop(struct mc_request *req)
 {
-	deactivate_fd(req->originating_fd, MCONSOLE_IRQ);
+	block_signals();
 	os_set_fd_block(req->originating_fd, 1);
 	mconsole_reply(req, "stopped", 0, 0);
 	for (;;) {
@@ -247,6 +247,7 @@ void mconsole_stop(struct mc_request *req)
 	}
 	os_set_fd_block(req->originating_fd, 0);
 	mconsole_reply(req, "", 0, 0);
+	unblock_signals();
 }
 
 static DEFINE_SPINLOCK(mc_devices_lock);