Staging: rtl8188eu: Fix warning of unnecessary parentheses.

This patch fixes the warning of "unnecessary parentheses" in file rtw_cmd.c.

Signed-off-by: Elena Oat <oat.elena@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>