With 64 gNB antenna elements the SRS channel IQ matrix exceeds the
ranges the SRS report code path was written for (272 PRGs * 2 UE ports
* 64 elements * 4 B = 136 KiB per report):

- unpack_nr_srs_report_tlv_value(): last_idx was int16_t, which
  overflows at report lengths >= 128 KiB, so the copy loop never ran
  and the report was silently dropped. Widen to int32_t and reject
  reports larger than the value buffer instead of overrunning it.
- pack/unpack_nr_srs_normalized_channel_iq_matrix():
  channel_matrix_size was uint16_t and wraps at 64 KiB, truncating the
  matrix. Widen to uint32_t and bound it by sizeof(channel_matrix).
- handle_nr_srs_measurements(): the SRS_IND_DEBUG print indexed the
  matrix with a uint16_t, which wraps for Nu*Ng*Np > 65535.

Assisted-by: Claude Code:claude-fable-5
Signed-off-by: Gabriele Gemmi <g.gemmi@northeastern.edu>