staging: rtl8192e: Remove unnecessary pre-declaration of struct net_device

Remove pre-declaration of struct.

Signed-off-by: Teddy Engel <engel.teddy@gmail.com>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/bb7d1aa7b336e4d68a30fd17dae7accfd2d5a26e.1718309120.git.engel.teddy@gmail.com


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