msm: pcie: update PCIe PHY sequence on MSM8992

PCIe PHY on MSM8992 requires different Vbg settings.
Therefore, update the PCIe PHY sequence on MSM8992.

Change-Id: If78c990b2c02cfc7b315061870260654f2f984cb
Signed-off-by: Tony Truong <truong@codeaurora.org>