pmdomain: imx: fix OF node refcount

for_each_child_of_node_scoped() decrements the reference count of the
nod after each iteration. Assigning it without incrementing the refcount
to a dynamically allocated platform device will result in a double put
in platform_device_release(). Add the missing call to of_node_get().

Cc: stable@vger.kernel.org
Fixes: 3e4d109ee8fc ("pmdomain: imx: gpc: Simplify with scoped for each OF child loop")
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Ulf Hansson <ulfh@kernel.org>