clk: sysfs: fix invalid JSON in clk_dump

[ Upstream commit c6e90997 ]

Add a missing comma so that the output is valid JSON format again.

Fixes: 9fba738a ("clk: add duty cycle support")
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>