staging: ks7010: Avoid clashing function prototypes

When built with Control Flow Integrity, function prototypes between
caller and function declaration must match. These mismatches are visible
at compile time with the new -Wcast-function-type-strict in Clang[1].

Fix a total of 27 warnings like these:

drivers/staging/ks7010/ks_wlan_net.c:2415:2: warning: cast from 'int (*)(struct net_device *, struct iw_request_info *, struct iw_point *, char *)' to 'iw_handler' (aka 'int (*)(struct net_device *, struct iw_request_info *, union iwreq_data *, char *)') converts to incompatible function type [-Wcast-function-type-strict]
        (iw_handler)ks_wlan_get_firmware_version,/* 3 KS_WLAN_GET_FIRM_VERSION */
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The ks_wlan_net Wireless Extension handler callbacks (iw_handler) use a
union for the data argument. Actually use the union and perform explicit
member selection in the function body instead of having a function
prototype mismatch. There are no resulting binary differences
before/after changes.

These changes were made partly manually and partly with the help of
Coccinelle.

Link: https://reviews.llvm.org/D134831 [1]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/8d2ceee1248b5a76e9b6c379f578e65482c91168.1667934775.git.gustavoars@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>