hnbgw: fix PLMN in g_hnb_cfg

To get 001-01, we need to encode the placeholder 0xf nibble.

Since recently, osmo-hnbgw cares about the PLMN in messages, in specific
cases: in upcoming CN pool tests, the PLMN is part of the algorithm that
picks the CN link. So let's encode 001-01 correctly.

Change-Id: I5299c521479dc25ea0f82d7d294d53942960d2cf
1 file changed