The function is declared and defined as inline and gcc6 will not
emit an external visible symbol for it. Master doesn't have this
problem anymore so let's just patch it here.
Fixes:
| /usr/src/debug/osmo-bts/0.4.3+gitAUTOINC+57ee780789-r1a2ff06d20-r18.18/git/tests/sysmobts/sysmobts_test.c:207: undefined reference to `l1if_ms_pwr_ctrl'
Holger Hans Peter Freyther