Properly set TA_VALID bit

Check Timing Advance validity and set corresponding bit for Immediate
Assignment message. Previously !polling was errorneously used (polling
bit has nothing to do with TA validity according to 3GPP TS 44.018 Table
10.5.2.16.1) which lead to TA being always valid as polling is always 0
in other parts of the code.

Change-Id: I5d7ecc7f71402b945cae99332be2ebc0b17b9d44
Related: OS#1526
1 file changed