staging: ks7010: avoid ks_sdio_card dependency in ks_wlan header

ks_wlan_private struct has a pointer to struct ks_sdio_card in its
fields. Because of that a forward declaration in needed in ks_wlan.h
header and also it makes necessary to have ks_sdio_card public in
a ks7010_sdio.h header. Changing this pointer into a void pointer
makes no longer necessary to have ks7010_sdio.h header as well as
removes the forward dependency in ks_wlan.h. Declaration of
ks_sdio_card has been moved to ks7010_sdio.c source file and To make
code cleaner inside this file a new ks7010_to_func function has been
added. The code has been updated to this changes.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>