transceiver: uhd: allow underrun flag to reset during timing alignment
transceiver: uhd: allow underrun flag to reset during timing alignment

Allowing the underrun flag to reset will prevent a single event from
causing large jumps in the transmit latency threshold. This should
keep unreasonable timing latencies from occurring (e.g. latencies of
20+ frames).

git-svn-id: 504cad4147f1e500be0a169b9f46375eaf875953@3981 19bc5d8c-e614-43d4-8b26-e1612bc8e597

0x7678/openbts-2.8,0x7678/openbts-multi-arfcn,fairwaves/openbts-2.8,0x7678/openbts-2.8,0x7678/openbts-multi-arfcn,0x7678/openbts-2.8,0x7678/openbts-2.8,ttsou/openbts-p2.8,ttsou/openbts-p2.8,fairwaves/openbts-2.8,kheimerl/vbts-openbts,0x7678/openbts-2.8,0x7678/openbts-multi-arfcn,0x7678/openbts-multi-arfcn,ttsou/openbts-p2.8,0x7678/openbts-multi-arfcn,kheimerl/vbts-openbts,fairwaves/openbts-2.8,kheimerl/vbts-openbts,ttsou/openbts-p2.8,fairwaves/openbts-2.8,fairwaves/openbts-2.8,ttsou/openbts-p2.8,kheimerl/vbts-openbts,kheimerl/vbts-openbts