staging: w35und: Inline MLMESendFrame() to wbsoft_tx()

The wbsoft_tx() function is a simple wrapper on top of MLMESendFrame() so
inline the latter to the former.

Cc: Lars Lindley <lindley@coyote.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Ruslan Pisarev <ruslan@rpisarev.org.ua>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>