camera: flash: add gpio based led flashlight driver

- Ported camera led gpio based flash driver from kernel 3.10 to
  kernel 4.9 for 8905
- media_entity_pads_init function are change from kernel 3.10 to 4.9
- media entity.function are change from kernel 3.10 to 4.9
- Add proper led_classdev name value as "flashlight" before registering
  led_classdev
- setting " led->cdev.flags |= LED_KEEP_TRIGGER" flags before registering
  led classdev
- call msm_led_torch_create_classdev for led_classdev registration.

Change-Id: Ibaffef4c7f2393108348472213c50339eda1beb8
Signed-off-by: Darshan Kumsi Srinivasa <darssr@codeaurora.org>