um: Fix uml_mconsole stop/go

commit 1a3a6a2a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>