drm/rockchip: dw_hdmi: filter regulator -EPROBE_DEFER error messages

When the avdd-0v9 or avdd-1v8 supply are not yet available, EPROBE_DEFER
is returned by rockchip_hdmi_parse_dt(). This causes the following error
message to be printed multiple times:

    dwhdmi-rockchip fe0a0000.hdmi: [drm:dw_hdmi_rockchip_bind [rockchipdrm]] *ERROR* Unable to parse OF data

Fix that by not printing the message when rockchip_hdmi_parse_dt()
returns -EPROBE_DEFER.

Fixes: ca80c4eb ("drm/rockchip: dw_hdmi: add regulator support")
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220926203752.5430-1-aurelien@aurel32.net