pci: layerscape: Fix the LUT and msi-map mismatch issue

In the current code, it doesn't reset the cursors of LUT entry and
StreamID at the beginning of the fixup, so it can result in LUT entry
setup and msi-map mismatch and LUT entries and StreamID leaking
when reload and fixup the DTB.
This patch move the initialization of LUT entry and StreamID cursors
to the beginning of the fixup to resolve the issues.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
[Rebased]
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>