drm/rockchip: dw_hdmi_qp: Fixup usage of enable_gpio member in main struct

drm/rockchip: dw_hdmi_qp: Fixup usage of enable_gpio member in main struct

The name of the enable_gpio member in struct rockchip_hdmi_qp is too
generic, as initially "borrowed" from downstream BSP code. Moreover,
this hasn't been really in use so far, since there is neither a DT
providing an "enable-gpios" property to any of the "hdmi" nodes, nor a
binding documenting it.

The actual purpose of this GPIO line is to control the voltage bias for
the HDMI TX data lines when switching between TMDS and FRL operating
modes.

A previous patch introduced the "frl-enable-gpios" property of the
RK3588 HDMI TX Controller binding, hence pass the updated string to
devm_gpiod_get_optional(), rename the struct member accordingly and set
it to a low level.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20251027222641.25066-3-laurent.pinchart@ideasonboard.com