[Fix](mluOpGenerateProposalsV2): fix core dump.

[mahxn0]

Thanks for your contribution and we appreciate it a lot. :rocket::rocket:

1. Motivation

Fix gpv2 workspace interface incorrect usage problem

2. Modification

kernels/generate_proposals_v2/generate_proposals_v2.cpp test/mlu_op_gtest/pb_gtest/src/zoo/generate_proposals_v2/generate_proposals_v2.cpp