cnss2: Clear PCIe remap window field during shutdown

The PCI remap window field is to store last remap window value
which needs to be cleared during during shutdown, otherwise
wrong value will be used in next powerup.

Change-Id: I69ea892aaf73a8f75967a4d245f5d1789e0e728c
Signed-off-by: Yue Ma <yuem@codeaurora.org>