clk: tegra: Refactor PLL programming code

Refactor the PLL programming code to make it useable by the new PLL types
introduced by Tegra114.

The following changes were done:

* Split programming the PLL into updating m,n,p and updating cpcon
* Move locking from _update_pll_cpcon() to clk_pll_set_rate()
* Introduce _get_pll_mnp() helper
* Move check for identical m,n,p values to clk_pll_set_rate()
* struct tegra_clk_pll_freq_table will always contain the values as defined
  by the hardware.
* Simplify the arguments to clk_pll_wait_for_lock()
* Split _tegra_clk_register_pll()

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