BUG: Fix SIMD f32 trunc test on s390x when baseline is none

[seiko2plus]

Partial backport of #24479

Relates to #24750

Fix the following test error:

self = <numpy.core.tests.test_simd_module.Test_SIMD_MODULE object at 0x3ff2e4e9bb0>
    def test_truncate_f32(self):
>       f32 = npyv.setall_f32(0.1)[0]
E       AttributeError: module 'numpy.core._simd.VX' has no attribute 'setall_f32'. Did you mean: 'setall_s32'?
self       = <numpy.core.tests.test_simd_module.Test_SIMD_MODULE object at 0x3ff2e4e9bb0>
../../../../BUILDROOT/numpy-1.26.0-1.fc40.s390x/usr/lib64/python3.12/site-packages/numpy/core/tests/test_simd_module.py:89: AttributeError

[charris]

Thanks Sayed.