common/abis: fix the use of deprecated e1inp_line_get() API
common/abis: fix the use of deprecated e1inp_line_get() API

We need curly braces becausee1inp_line_get2() is basically a macro
that calls OSMO_ASSERT(), which in its turn contains an 'if' stmt.

Change-Id: I41a5fd13a7fa40e16bcf1a8099624b654274cee3

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts