use _NUM_CHREQ_T to define the size of ctype_by_chreq

Make it future compatible for changes. Otherwise it will break
when additional enums are adding to chreq in libosmocore.
Depends on libosmocore Id67ba8de89dd6288e449197438e9e1c5d7f5a134

Change-Id: I2acab2af8d67bccb2bc495512c1f259ae649a832
1 file changed