ARM: dts: msm: add PMIC revid source property for flash LED

Add PMIC revid source property, in order to differentiate
between PMIC subtypes and revisions for flash LED.

Change-Id: Idd93f2c091fcf5c261e7f6c996c149a874fc3e83
Signed-off-by: Jigarkumar Kishorkumar Zala <j_zala@codeaurora.org>