i2c_elan: Support I2C Elan devices

They are not HID devices as they need special polling and interpreting. As
a result only descriptor is shared with other i2c HID devices. So it's easier
to have it as a separate driver.

Partially based on FreeBSD ietp driver

Change-Id: Iddc64d216eefeda235a1b15521cba9189dd2ffd8
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6660
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>