mwifiex: sdio: fix use after free issue for save_adapter

If we have sdio work requests received when sdio card reset is
happening, we may end up accessing older save_adapter pointer
later which is already freed during card reset.
This patch solves the problem by cancelling those pending requests.

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