pwm-backlight: Enable/disable the PWM before/after LCD enable toggle.

pwm-backlight: Enable/disable the PWM before/after LCD enable toggle.

Before this patch the enable signal was set before the PWM signal and
vice-versa on power off. This sequence is wrong, at least, it is on
the different panels datasheets that I checked, so I inverted the sequence
to follow the specs.

For reference the following panels have the mentioned sequence:
  - N133HSE-EA1 (Innolux)
  - N116BGE (Innolux)
  - N156BGE-L21 (Innolux)
  - B101EAN0 (Auo)
  - B101AW03 (Auo)
  - LTN101NT05 (Samsung)
  - CLAA101WA01A (Chunghwa)

Signed-off-by: Enric Balletbo i Serra <[email protected]>
Acked-by: Daniel Thompson <[email protected]>
Acked-by: Jingoo Han <[email protected]>
Acked-by: Thierry Reding <[email protected]>
Signed-off-by: Lee Jones <[email protected]>