media: v4l2-common: Add legacy camera sensor clock helper

media: v4l2-common: Add legacy camera sensor clock helper

The recently introduced devm_v4l2_sensor_clk_get() helper aims at
simplifying sensor drivers by centralizing clock handling code, as well
as reducing cargo-cult and deprecated behaviour.

A set of drivers implement external clock handling in a non-standard
way. This can't be changed as there is a high risk of breaking existing
platforms, but keeping the code as-is creates a risk of new drivers
copying deprecated behaviour.

To fix this, introduce a new devm_v4l2_sensor_clk_get_legacy() helper
and use it in those driver. Compared to devm_v4l2_sensor_clk_get(), the
new helper takes the "clock-frequency" property into account and sets
the external clock rate on OF platforms, and adds the ability to specify
a fixed default or fallback clock rate in case the "clock-frequency"
property is not present.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Mehdi Djait <mehdi.djait@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>