qcacld-3.0: Don't create wifi-aware0 interface if NAN is not supported

Currently, NAN discovery interface(wifi-aware0) is created if both
host and firmware support NAN separate vdev feature. But NAN
feature capability(gEnableNanSupport) is the master of these
capabilities. Don't create wifi-aware0 if gEnableNanSupport is
disabled.
Also, don't allow NAN iface creation for the kernels less
than 4.14 as NAN interface is allowed by kernel only from 4.14.

Change-Id: Iaf10974c373b2a77d2c24a78540910f78a3dc768
CRs-Fixed: 2706997