mwifiex: use pci_dma_sync_single* APIs

On some platforms, driver is unable read sleep cookie signature even
if firmware has written it through DMA. The problem is fixed by using
pci_dma_sync_single* APIs while reading DMA buffer shared with firmware.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>