implement nanoBTS frequency error test

This helps us to detect the frequency error of BS-11 if it is located
next to the nanoBTS 900.

If 'ipaccess-config -l' is called, it will produce a report like
<0020> ipaccess-config.c:85 TEST REPORT: test_no=0x42 test_res=0
<0020> ipaccess-config.c:108 ==> ARFCN  220, Frequency Error     22
<0020> ipaccess-config.c:108 ==> ARFCN    1, Frequency Error    -37
<0020> ipaccess-config.c:108 ==> ARFCN   10, Frequency Error      0
<0020> ipaccess-config.c:108 ==> ARFCN   20, Frequency Error     11
<0020> ipaccess-config.c:108 ==> ARFCN   53, Frequency Error      5
<0020> ipaccess-config.c:108 ==> ARFCN   63, Frequency Error     -4
<0020> ipaccess-config.c:108 ==> ARFCN   84, Frequency Error     11
<0020> ipaccess-config.c:108 ==> ARFCN  101, Frequency Error      0
<0020> ipaccess-config.c:108 ==> ARFCN  123, Frequency Error    -52

where in this case the ARFCN 123 is the BS-11 with a frequency error
larger than all the other (regular) BTS in the vicinity.
4 files changed
tree: 860d6850bb55ca10224ef417803aedee27958d52
  1. linux-kernel/
  2. openbsc/
  3. wireshark/