mwifiex: use pci_alloc/free_consistent APIs for PCIe

This patch uses pci_alloc_consistent and pci_free_consistent
APIs for mwifiex_pcie driver. Consistent DMA memory is allocated
for TX, RX and event rings. Command buffer and command response
buffer also uses map/unmap memory APIs to download commands and
get command responses.

Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>