The hw-blinking of the LED controller in the Whiskey Cove PMIC can also
be used for a hw-breathing effect.

As discussed during review of v2 of the submission of the new
leds-cht-wcove driver, the LED subsystem already supports breathing mode
on several other LED controllers using the hw_pattern interface.

Implement a pattern_set callback to implement breathing mode modelled
after the breathing mode supported by the SC27xx breathing light and
Crane EL15203000 LED drivers. The Whiskey Cove PMIC's breathing mode
is closer to the EL15203000 one then to the SC27xx one since it does
not support staying high / low for a specific time, it only supports
rise and fall times.

As such the supported hw_pattern and the documentation for this is almost
a 1:1 copy of the pattern/docs for the EL15203000 breathing mode.
Suggested-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Link: https://lore.kernel.org/all/6beed61c-1fc6-6525-e873-a8978f5fbffb@gmail.com/Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230430195952.862527-4-hdegoede@redhat.comSigned-off-by: Lee Jones <lee@kernel.org>