net/tap: fix build for glibc < 2.24

net/tap: fix build for glibc < 2.24

When trying to compile with glibc < 2.24 that doesn't
support SOL_NETLINK it will cause compilation failure:

drivers/net/tap/tap_netlink.c:70:17: error:
 'SOL_NETLINK' undeclared (first use in this function)
  setsockopt(fd, SOL_NETLINK, NETLINK_EXT_ACK, &one, sizeof(one));

The glibc commits adds the SOL_NETLINK support:
https://github.com/bminor/glibc/commit/f9b437d5efce93800b51ad2a437c8b1c9

Fixes: 647909bcf34b ("net/tap: use netlink extended ack support")

Signed-off-by: Raslan Darawsheh <rasland@mellanox.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>