gpu: drm: exynos: hdmi: eliminate uses of of_node_put()

Utilize the __free() cleanup handler within the hdmi_get_phy_io function
to automatically release the device node when it is out of scope.
This eliminates the manual invocation of of_node_put(), reducing the
potential for memory leaks.

The modification requires initializing the device node at the beginning
of the function, ensuring that the automatic cleanup is safely executed.

Consequently, this removes the need for error cleanup paths that utilize
goto statements and the jump to out is no longer necessary.

Suggested-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Shivani Gupta <shivani07g@gmail.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>