clk: tegra: Make tegra_clk_super_mux_ops static

Fix sparse warning:

drivers/clk/tegra/clk-super.c:124:22:
 warning: symbol 'tegra_clk_super_mux_ops' was not declared. Should it be static?

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>