clk: tegra: pllc and pllxc should use pdiv_map

The pllc and pllxc code weren't always using the correct pdiv_map to
map between the post divider value and the hw p field. This could result
in illegal values being programmed in the hw.

Signed-off-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>