MFC r311649:

MFC r311649:

Fix the following clang 4.0.0 warning in ngatm's snmp_atm.c:

    contrib/ngatm/snmp_atm/snmp_atm.c:173:6: error: logical not is only
    applied to the left hand side of this bitwise operator
    [-Werror,-Wlogical-not-parentheses]
            if (!ifmr.ifm_status & IFM_AVALID) {
                ^                ~

Obviously, the masking needs to be done before the logical not
operation.  Add parentheses to make it so.

git-svn-id: svn://svn.freebsd.org/base/stable/9@311937 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f