pci: msm: msm_pcie_iatu_config API clean

Get rid of access to pciedev_table. Update data type
for bdf from unsigned long to u32. Prevent iATU config
for root port BDF. Do not save config values to rc_shadow
as iATU is configured dynamically.

Change-Id: I9e7254d1e6d91869db71c71f1c5b699a4d6376f4
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>