msm: camera: Use current property to fetch brightness

For LED flash, Currently, <qcom,max-current> property is used to extract
maximum brightness. Using maximum value may cause current drain from pmic.
<qcom,current> property refers to optimal value. Use optimal value
instead of maximum value.

Change-Id: Iedda300149abe67cf7daa70d3309b80ac67a14d4
Signed-off-by: Sreesudhan Ramakrish Ramkumar <srramku@codeaurora.org>