firmware: meson_sm: fix device leak at probe

Make sure to drop the reference to the secure monitor device taken by
of_find_device_by_node() when looking up its driver data on behalf of
other drivers (e.g. during probe).

Note that holding a reference to the platform device does not prevent
its driver data from going away so there is no point in keeping the
reference after the helper returns.

Fixes: 8cde3c21 ("firmware: meson_sm: Rework driver as a proper platform driver")
Cc: stable@vger.kernel.org	# 5.5
Cc: Carlo Caione <ccaione@baylibre.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20250725074019.8765-1-johan@kernel.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>