ARM: hisi: check of_iomap and fix missing of_node_put

of_find_compatible_node() returns a device node with refcount incremented
and thus needs an explicit of_node_put(). Further relying on an unchecked
of_iomap() which can return NULL is problematic here, after all ctrl_base
is critical enough for hix5hd2_set_cpu() to call BUG() if not available
so a check seems mandated here.

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
0002 Fixes: commit 06cc5c1d ("ARM: hisi: enable hix5hd2 SoC")
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>