clk: tegra: Add fields for override bits

PLLM can have override bits in the PMC. Describe those in the PLL parameters.

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>