When platform_get_irq fails, we should return dpaux->irq
instead of -ENXIO.

Fixes: 6b6b6042 ("drm/tegra: Add eDP support")
Signed-off-by: Yangtao Li <frank.li@vivo.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230710032355.72914-13-frank.li@vivo.com