cnss2: Get MSI base data directly from MSI description

Instead of reading from PCI config space, get MSI base data directly
from MSI description of PCI framework. This can avoid knowing the
device capability (32-bit or 64-bit) which results different config
space offset for driver to read.

Change-Id: Id52f2f3f85928f269da9f01aaf4bc22c5d1cf581
CRs-fixed: 2025945
Signed-off-by: Yue Ma <yuem@codeaurora.org>