ARM: OMAP2+: add missing call to of_node_put()

In one of the error paths of the for_each_child_of_node() loop,
add missing call to of_node_put().

Fix the following coccicheck warning:
./arch/arm/mach-omap2/omap_hwmod.c:2132:1-23: WARNING: Function
"for_each_child_of_node" should have of_node_put() before return around
line 2140.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>