Revert "[OpenMP] Simplify parallel reductions (#70983)"

This reverts commit e9a48f9e05c103a235993c6b15a2c36442a2ddc1 because it breaks
3 sollve 5.0 tests:

test_loop_reduction_and_device.c
test_loop_reduction_bitand_device.c
test_loop_reduction_multiply_device.c

GitOrigin-RevId: db37d25c5363729c425535549e5d6f49a65e24ff
2 files changed