mesh: Transport tx seg_o overflow
mesh: Transport tx seg_o overflow

Increases the transport segmentented tx seg_o counter to 6 bits to avoid
overflow when sending 32 segments. The check in the send loop would
previously never be false, which causes segments to repeat
unnecessarily.

this is port of e1c6ea9241e21942965eb66a62f13624c5528905

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