arm/dt: msm8974: add auto focus support for s5k3l1yx camera sensor

To support auto focus function, s5k3l1yx camera sensor node
requires CAM_STANDBY GPIO and actuator instance to be assigned.
The change is derived from the s5k3l1yx sensor node configuration in CDP.

Change-Id: I422cf9f4a163fab38fcf2cc18c132bc88c9b0d34
Signed-off-by: Ilia Lin <ilialin@codeaurora.org>