[openmp] Fix enumeration build issue for openmp library

integer value 40962 is outside the valid range of values [0, 31] for this enumeration type [-Wenum-constexpr-conversion]` (Issue #57022)

turn on -Wno-enum-constexpr-conversion to buy some time to fix the more egregious issue in hsa_agent_into_t and hsa_amd_agent_info_t interfaces.

relates to https://reviews.llvm.org/D131307/new/

Differential Revision: https://reviews.llvm.org/D131477