mwifiex: do not enable PCIe interrupt in Power Save sleep state

Enabling PCIe host interrupt may accidently wake up the card
when it's in sleep.

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>