i2c: mpc: Removal of of_node_put with __free for auto cleanup

Remove of_node_put from node_ctrl and node struct device_nodes.
Move the declaration to initialization for ensuring scope sanity.

Suggested-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Abhinav Jain <jain.abhinav177@gmail.com>
Reviewed-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>