Use lazy initialization in unit tests.
Static initialization has no guaranteed order, which may cause test listing to be initialized before the list of kernels.
This fixes unit tests
- matmul_clamp_f32_bf16p_bf16p_test
- matmul_clamp_f16_bf16p_bf16p_test
Signed-off-by: Jens Elofsson jens.elofsson@arm.com