staging: r8188eu: hal data's interfaceIndex is never read

interfaceIndex in struct hal_data_8188e is set but not used.
It can be removed.

Acked-by: Michael Straube <straube.linux@gmail.com>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211205151251.6861-7-martin@kaiser.cx


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