clk: tegra: pll: Improve PLLM enable-state detection

clk: tegra: pll: Improve PLLM enable-state detection

Power Management Controller (PMC) can override the PLLM clock settings,
including the enable-state. Although PMC could only act as a second level
gate, meaning that PLLM needs to be enabled by the Clock and Reset
Controller (CaR) anyways if we want it to be enabled. Hence, when PLLM is
overridden by PMC, it needs to be enabled by CaR and ungated by PMC in
order to be functional. Please note that this patch doesn't fix any known
problem, and thus, it's merely a minor improvement.

Link: https://lore.kernel.org/linux-arm-kernel/20191210120909.GA2703785@ulmo/T/
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20200709172057.13951-1-digetx@gmail.com
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>