mwifiex: cancel pcie/sdio work in remove/shutdown handler

The last command used to shutdown firmware might be timeout,
and trigger firmware dump in asynchronous pcie/sdio work.

The remove/shutdown handler will continue free core data
structure private/adapter, which might be dereferenced in
pcie/sdio work, finally crash the kernel.

Sync and Cancel pcie/sdio work, could be a fix for above
cornel case. In this way, the last command timeout could
be handled properly.

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