staging: r8188eu: BW40_24G_Diff is set but not used

The BW40_24G_Diff array is set but not used. Remove it.

Acked-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220105083426.177128-6-martin@kaiser.cx


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