Tegra210 QSPI clock output has divider DIV2_SEL which will be enabled
when using DDR interface mode.

This patch adds clock ID for this to dt-binding.
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Link: https://lore.kernel.org/r/1608585459-17250-2-git-send-email-skomatineni@nvidia.comSigned-off-by: Mark Brown <broonie@kernel.org>