clk: tegra: Fix build error without CONFIG_PM_SLEEP

If CONFIG_PM_SLEEP is n, build fails:

drivers/clk/tegra/clk-tegra210.c:3426:13: error:
 tegra210_clk_suspend undeclared here (not in a function); did you mean tegra_clk_ndspeed?
  .suspend = tegra210_clk_suspend,
             ^~~~~~~~~~~~~~~~~~~~
             tegra_clk_ndspeed
drivers/clk/tegra/clk-tegra210.c:3427:12: error:
 tegra210_clk_resume undeclared here (not in a function); did you mean tegra210_clk_suspend?
  .resume = tegra210_clk_resume,

Use ifdef to guard this.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 27d10d548c04 ("clk: tegra: Add suspend and resume support on Tegra210")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>