cnss2: Make sure the write to remap window register take effect

Since PCIe remap window register access and actual PCIe device
register access may go through different NoCs, read it back after
writing to remap window register to make sure it has taken effect.
This is able to avoid NOC errors when accessing the actual device
register which the remap window value applies to.

Change-Id: I65848758250fb9e6e1cbe513932c64b8303a8e98
Signed-off-by: Yue Ma <yuem@codeaurora.org>