mtd: hyperbus: hbmc-am654: fix an OF node reference leak

In am654_hbmc_platform_driver, .remove() and the error path of .probe()
do not decrement the refcount of an OF node obtained by
  of_get_next_child(). Fix this by adding of_node_put() calls.

Fixes: aca31ce9 ("mtd: hyperbus: hbmc-am654: Fix direct mapping setup flash access")
Signed-off-by: Joe Hattori <joe@pf.is.s.u-tokyo.ac.jp>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>