drivers: led: Implemented PCA9533 driver with PM support

• Supports led_on/off, led_set_brightness (0–100 %, 152 Hz default),
  and led_blink (7 ms – 1.685 s) with automatic sharing of the two
  on-chip PWM engines; returns –EBUSY when a third distinct pair is
  requested.

• Includes basic runtime-PM boilerplate to honour power-domain control;
  the device itself has no dedicated low-power states.

Signed-off-by: Van Petrosyan <van.petrosyan@sensirion.com>