rlcmac: Handle properly LI=0 in GPRS data blocks and identify spare bits
The previous handling of LI=0 was a confusion with the LI=0 meaning from EGPRS (see TS 44.060 B.8.2 Example 2) data block.
The previous handling of LI=0 was a confusion with the LI=0 meaning from EGPRS (see TS 44.060 B.8.2 Example 2) data block.