staging: r8188eu: use ieee80211 defines for back action codes

Replace the driver-specific defines for back action codes with the defines
from ieee80211.h.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/20220602194807.281115-2-martin@kaiser.cx


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