soc: bcm: brcmstb: Add of_node_put() in pm-mips

Fix following coccicheck warning:
./drivers/soc/bcm/brcmstb/pm/pm-mips.c:404:1-23: WARNING: Function
for_each_matching_node should have of_node_put() before goto or break

Early exits from for_each_matching_node should decrement the
node reference counter.

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>