bssgp: Fix IMSI buffer size (Coverity)

Currently the size of the IMSI pointer is used instead of the size of
the talloc'ed buffer.

This commit changes the call to gsm48_mi_to_string to use the same
value that has been used with talloc_zero_size(). The length is
changed to 17 since that value is used for GSM_IMSI_LENGTH in
openbsc.

Fixes: Coverity CID 1040663
Sponsored-by: On-Waves ehf
1 file changed