clk: tegra: Read correct IDDQ register in PLL_SS registration

This fixes a bug in tegra_clk_register_pllss() which mistakenly assume
the IDDQ register is the PLL base address.

Signed-off-by: Bill Huang <bilhuang@nvidia.com>
Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>