nimble/ll: Fix legacy scanning with ext adv support enabled
nimble/ll: Fix legacy scanning with ext adv support enabled

LL will try to unref aux_data for an ADV_EXT_IND PDU which was received
while legacy scanning was active. This is not correct since such PDU
does not have aux_data allocated and we'll hit an assert.

We can just skip that check in LL context since ISR will mark such PDU
as ignored and it can be handled properly by LL.

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