counter: stm32-timer-cnt: fix device_node handling in probe_encoder()

Device nodes accessed via of_get_compatible_child() require
of_node_put() to be called when the node is no longer required to avoid
leaving a reference to the node behind, leaking the resource.

In this case, the usage of 'tnode' is straightforward and there are no
error paths, allowing for a single of_node_put() when 'tnode' is no
longer required.

Cc: stable@vger.kernel.org
Fixes: 29646ee3 ("counter: stm32-timer-cnt: add checks on quadrature encoder capability")
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20241027-stm32-timer-cnt-of_node_put-v1-1-ebd903cdf7ac@gmail.com


Signed-off-by: William Breathitt Gray <wbg@kernel.org>