staging: r8188eu: Fix unused variable warnings

A previous set of patches were test compiled with one of the configuration
variables not set. As a result, a number of unused variables were left in the
code.

In several instances, declaration of the unused variable was the only statement
inside ifdef .. endif pairs. In those cases, the entire block was removed.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>