msm: pcie: add support to get PCIe PHY init sequence from DT

PCIe PHY varies between each chipset. Thus, the PHY init sequence on
each of these chipsets are also different. Therefore, add the support
to read PCIe PHY init sequence from devicetree.

Change-Id: I21c2ce2b7d3bf1541a5d3580db4bc40497701095
Signed-off-by: Tony Truong <truong@codeaurora.org>