Input: fix EVIOCGNAME/JSIOCGNAME regression

Commit 3d5cb60e ("Input: simplify name handling for certain input
handles") introduced a regression for the EVIOCGNAME/JSIOCGNAME
ioctl.

Before this, patch, the platform device's name was given back to
userspace which was good to identify devices. After this patch, the
device is ("event%d", minor) which is not descriptive at all.

This fixes the behaviour by taking dev->name.

Reported-by: Sven Neumann <s.neumann@raumfeld.com>
Signed-off-by: Daniel Mack <daniel@caiaq.de>
Reviewed-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>