mesh: Transport tx fields overflow
mesh: Transport tx fields overflow

The transport segmented TX nack and seg_pending fields must be at least
6 bits to avoid overflow for 32 segment messages. This change rearranges
the seg_tx fields to gather all state flag fields in one byte, while
making the counter fields whole bytes.

this is port of 4a2e56d42a432f603df0ae3101b00f4a0fe350e6

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