int_osx_receive_prim() in gsm-fw/gpf/osx/osx.c: there was an error in the reconstruction of this function from disassembly in the logic that implements special handling for MPHC_RXLEV_REQ messages. The code is now fixed to properly match what the binary object version does; with this fix the firmware now performs the power measurement phase correctly and the initial network registration succeeds.

L1S (l1_cmplx.c specifically) calls these 3 functions which are normally
defined in the DL protocol stack entity:

dll_dcch_downlink()
dll_read_dcch()
dll_read_sacch()

If we are building L1 standalone (without the G23 protocol stack), we need
to provide stubs for these functions.