Input: uinput - add devname alias to allow module on-demand load

Recent modprobe and udev versions allow to create device nodes
for modules which are not loaded. Only the first access will cause
the in-kernel module loader to pull-in the module. Systems which
never access the device node will not needlessly load the module,
and no longer need init scripts or other facilities to unconditionally
load it.

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>