Input: cros_ec_keyb - send 'scancodes' in addition to key events

To let userspace know what 'scancodes' should be used in EVIOCGKEYCODE
and EVIOCSKEYCODE ioctls, we should send EV_MSC/MSC_SCAN events in
addition to EV_KEY/KEY_* events. The driver already declared MSC_SCAN
capability, so it is only matter of actually sending the events.

Link: https://lore.kernel.org/r/X87aOaSptPTvZ3nZ@google.com
Acked-by: Rajat Jain <rajatja@google.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>