staging: r8188eu: remove DBG_88E macro definition

Remove DBG_88E macro definition as it has no remaining callers within
the driver. This is part of the ongoing effort to cleanup the driver to
use standard debug mechanisms where appropriate.

Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20220216010709.791-11-phil@philpotter.co.uk


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