ARM: dts: msm: Change LAB precharge time to 500us in pmicobalt

Set LAB's precharge time to max 500us to optimize the precharge
behavior as suggested in the hardware documentation.

CRs-Fixed: 1084297
Change-Id: I118f4254686caf498087847916b7710662ab31e7
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>