staging: r8188eu: Remove all calls to _rtw_spinlock_free()

This routine is empty, thus all calls to it can be removed.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Link: https://lore.kernel.org/r/20210805183717.23007-4-Larry.Finger@lwfinger.net


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>