msm: pcie: support iATU for Synopsys 4.80a core

Unlike previous versions, PCIe 4.80a core has a
dedicated space for iATU (internal address
translation unit). Update PCIe bus driver to
support the new iATU logic.

Change-Id: I467a4492a067fc8e24e3cfbd67098daa3c800783
Signed-off-by: Tony Truong <truong@codeaurora.org>