staging: rtl8188eu: remove else after return

Remove else after return in rtl88eu_dm_antenna_diversity() to improve
readability and clear a checkpatch warning.

WARNING: else is not generally useful after a break or return

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20200105194936.5477-1-straube.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>