Add support for IT8603E.

This closes bug #57861:
https://bugzilla.kernel.org/show_bug.cgi?id=57861

[JD: Fixes and clean-ups.]
Signed-off-by: NRudolf Marek <r.marek@assembler.cz>
Signed-off-by: NJean Delvare <khali@linux-fr.org>