Currently the channel combination II is used for TCH/H, which
allows only one lchan to be allocated. The reason is that it
saves a bit of CPU by disabling UL burst detection on lchan 1.
There is also the channel combination III, which allows to
increase channel capacity, providing two lchans on a single
TCH/H timeslot.
Ideally we should implement some dynamic II <-> III switching
depending on the network load level. But for now this change
replaces the channel combination of TCH/H by III, until dynamic
switching is implemented.
Fixes issue: https://osmocom.org/issues/1795
Change-Id: I8fd4abb42c153fcd26bcfe22a2554b5c2d02d810