cnss2: Enable io-coherency

Don't disable 'io-coherency' by default in cnss2 driver. PCI device
tree property "dma-coherent" controls this feature.

Change-Id: Iba4505cd011950ddaed1115ec32fd609f49aa415
Signed-off-by: Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>