soc/tegra: Add support for 32 kHz blink clock

Tegra PMC has blink control to output 32 kHz clock out to Tegra blink
pin. Blink pad DPD state and enable controls are part of Tegra PMC
register space.

Currently Tegra clock driver registers blink control by passing PMC
address and register offset to clk_register_gate which performs direct
PMC access during clk_ops and with this when PMC is in secure mode, any
access from non-secure world does not go through.

This patch adds blink control registration to the Tegra PMC driver using
PMC specific clock gate operations that use tegra_pmc_readl() and
tegra_pmc_writel() to support both secure mode and non-secure
mode PMC register access.

Tested-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>