Input: cros_ec_keyb - cleanup use of dev

In cros_ec_keyb we stored "dev" in "struct cros_ec_keyb", but this was
the EC's dev pointer and not the keyboard's.  Let's clean this up to
make it the keyboard's dev pointer.  This could be useful in future
patches but also has the nice effect of changing a few printouts to
include the name of the keyboard device instead of the EC device, so we
will see:

[    1.224648] cros-ec-keyb ff110000.spi:ec@0:keyboard-controller: valid_keys[00] = 0x14

instead of:

[    1.224505] cros-ec-spi spi0.0: valid_keys[00] = 0x14

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>