BTS_Tests: fix log line (AGCH->PCH)

The testcase TC_pcu_data_req_imm_ass_pch uses the PCH to transmit the
IMMEDIATE ASSIGNMENT message but the log line mentions the AGCH.

Related: OS#5927
Change-Id: I7cb8d91f2c3f92009d33134167eab856ee02fdab
1 file changed