Staging: rtl8723au: rtw_mlme_ext: Remove unnecessary test expression

Logical and-ing of a struct and its member should be replaced by the
member only as the struct has already been NULL tested before.

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Reviewed-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>