HID: input: generic hidinput_input_event handler

The hidinput_input_event() callback converts input events written from
userspace into HID reports and sends them to the device. We currently
implement this in every HID transport driver, even though most of them do
the same.

This provides a generic hidinput_input_event() implementation which is
mostly copied from usbhid. It uses a delayed worker to allow multiple LED
events to be collected into a single output event.
We use the custom ->request() transport driver callback to allow drivers
to adjust the outgoing report and handle the request asynchronously. If no
custom ->request() callback is available, we fall back to the generic raw
output report handler (which is synchronous).

Drivers can still provide custom hidinput_input_event() handlers (see
logitech-dj) if the generic implementation doesn't fit their needs.

Signed-off-by: Stefanescu Cristian <howerkraft@gmail.com>

Conflicts:
	drivers/hid/hid-input.c

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Michael Wright <michaelwr@google.com>
Change-Id: I89ccc3f675b3e8a7bbd812a6ebe12588d737cfd6
Signed-off-by: Stefanescu Cristian <howerkraft@gmail.com>