mwifiex: fix driver init failure under memory pressure

64k Tx and Rx buffers are allocated during driver initialization
for SDIO level data aggregations. When host is under memory
pressure situation, kzalloc() request for 64k may fail.

We will try allocating 32k buffers and disable our rx single port
aggreagation feature in this situation.

If the allocation still fails, we will disable our sdio multport
aggregation feature as well. In this way, we will transmit and
receive packets one by one, thus reduce the demand for big
memory.

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