leds: flash: Add support for flash/strobe duration

Add support for the new V4L2_CID_FLASH_DURATION control to the LEDs
driver.

Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
Link: https://lore.kernel.org/r/20250507-ov9282-flash-strobe-v4-2-72b299c1b7c9@linux.dev


Signed-off-by: Lee Jones <lee@kernel.org>