msm: pcie: get PHY stts offset from device tree on sdm845 & sdxpoorwills

Use the offset defined in device tree since every
PCIe PHY IP has a different status register. Add
PHY status offset entry for sdm845 and sdxpoorwills
device tree.

Change-Id: If975d843e24e74d99c01411a90940e76ee41a0a6
Signed-off-by: Tony Truong <truong@codeaurora.org>