wil6210: support devices with different PCIe bar size

wil6210 devices can have different PCIe bar size, hence get the
bar size from PCIe device instead of using a constant bar size.

Signed-off-by: Maya Erez <qca_merez@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>