staging: wilc1000: introduce struct wilc_sdio for sdio data

This patch introduces struct wilc_sdio for sdio driver data. The wilc_sdio is
allocated and set as driver data when the sdio is probed and deallocated when
the sdio is removed.

Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>