mwifiex: disable MSIx interrupt for 8997 chipset

Sometimes MSIx interrupts are received out of order on multi-core
system. This creates a problem when there is a race between data
packet and SLEEP event from firmware. We will disable MSIx interrupt
mode to solve the problem and go with MSI mode.

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