omapdrm: encoder-tpd12s015: keep ls_oe_gpio high

For OMAP4 CEC support the CEC pin should always be on. So keep
ls_oe_gpio high all the time in order to support CEC.

Background: even if the HPD is low it should still be possible
to use CEC. Some displays will set the HPD low when they go into standby or
when they switch to another input, but CEC is still available and able
to wake up/change input for such a display.

This is explicitly allowed by the CEC standard.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>