EDAC, altera: Add missing of_node_put()

The call to of_parse_phandle() returns a node pointer with refcount
incremented thus it must be explicitly decremented here after the last
usage.

Signed-off-by: Huang Zijiang <huang.zijiang@zte.com.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thor Thayer <thor.thayer@linux.intel.com>
Cc: James Morse <james.morse@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: wang.yi59@zte.com.cn
Link: https://lkml.kernel.org/r/1550126347-27984-1-git-send-email-huang.zijiang@zte.com.cn