build: simplify check for WITH_MACVTAP
build: simplify check for WITH_MACVTAP

macvtap support was added to the Linux kernel in 2.6.33. libvirt
checked for this by looking for MACVLAN_MODE_BRIDGE and IFLA_VF_MAX in
linux/if_link.h. This hasn't been necessary for a very long time, so
just gate on platform == 'linux' (and be sure to complain if someone
tries to enable it on a non-Linux platform).

Signed-off-by: Laine Stump <c23361c43fbf79fed83e8b76173707b083d6caf5@redhat.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

nertpinx/libvirt,jfehlig/libvirt,nertpinx/libvirt,crobinso/libvirt,libvirt/libvirt,jfehlig/libvirt,nertpinx/libvirt,crobinso/libvirt,crobinso/libvirt,olafhering/libvirt,libvirt/libvirt,crobinso/libvirt,zippy2/libvirt,libvirt/libvirt,zippy2/libvirt,jfehlig/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,olafhering/libvirt,libvirt/libvirt,jardasgit/libvirt,jfehlig/libvirt,zippy2/libvirt,nertpinx/libvirt,jardasgit/libvirt,jardasgit/libvirt,olafhering/libvirt,zippy2/libvirt,jardasgit/libvirt