cnss2: Disable PCIe bus master bit before save config space

There may be a issue if save PCIe config space with bus master
enabled. During resume, since the bit will be restored first,
device will think master is ready and then trigger MSI for some
events, but actually MSI config has not been restored yet which
will mask the MSI. To avoid this, clear the bus master bit before
save config space and the bit will be enabled at a later time.

Change-Id: If1674e7a4575ed0c190994e3d840fc83f90326b9
Signed-off-by: Yue Ma <yuem@codeaurora.org>