staging: r8188eu: remove unused macro IS_FW_81xxC

The macro IS_FW_81xxC is not used. Remove it.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20211205171342.20551-11-straube.linux@gmail.com


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