Staging: rtl8188eu: core: rtw_mlme.c: Remove NULL test before vfree

The function vfree tests whether the argument is NULL and returns
immediately. So NULL test before vfree is not needed. Also remove braces
around if branch as they are no longer needed.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>