mwifiex: handle error if IRQ request fails in mwifiex_sdio_of()

When this failure occurs, we will clear card->plt_wake_cfg so that
device would initialize without wake up on external interrupt feature.
This feature specific code in suspend and resume handlers will be
skipped.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>