nimble/ll_scan: Set filter duplicate only when controller allowed
nimble/ll_scan: Set filter duplicate only when controller allowed

If BLE_LL_NUM_SCAN_DUP_ADVS is 0 then never set filter duplicats in
scansm as it does not makes sense.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble