nimble/ll: Use bigger LL task stack with ext adv
nimble/ll: Use bigger LL task stack with ext adv

This was removed in 275718ac but as it turns out, we need more stack for
extended and (especially) periodic advertising when running on CM0.
120 words give us few words to spare when running all features on CM0.

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