pcu: Rewrite GPRS_Components functions to use pre-decoded RLCMAC blocks coming from PCUIF

This is only a step towards a major set of changes.
This specific commit changes internal implementation of functions to stay
compatible with existing tests.
Later on, changes will be modified to use the new altsteps directly.

Related: OS#4927
Change-Id: Iecc33565fdc673e3499db12a0d4e0587290cfd45
2 files changed