msm: camera: sensor: Validate destination step position

dest_step_position is sent from userspace and is used in
kernel to calculate the final DAC value.
dest_step_position must be validated against total steps.
Actuator will have an unexpected behavior if lens value is
programed to actuator based on invalid dest_step_position.

CRs-Fixed: 1102580
Change-Id: Idcd97043d3bd583d8577233d446a99d1829a4ee6
Signed-off-by: Rajesh Bondugula <rajeshb@codeaurora.org>