Support for AArch32 execution state

KlieidAI is not expected to support AArch32 execution state, but right now instead of erroring out with a message from here: https://gitlab.arm.com/kleidi/kleidiai/-/blob/main/examples/matmul_clamp_f16_f16_f16p/matmul_clamp_f16_f16_f16p.cpp?ref_type=heads#L16 that file must be compiled for AArch64, there are examples such as file: https://gitlab.arm.com/kleidi/kleidiai/-/blob/main/kai/ukernels/matmul/pack/kai_lhs_quant_pack_qsi8d32p_f32.c?ref_type=heads that doesn't have any guards but calls method kai_cast_fp16_fp32() here: https://gitlab.arm.com/kleidi/kleidiai/-/blob/main/kai/ukernels/matmul/pack/kai_lhs_quant_pack_qsi8d32p_f32.c?ref_type=heads#L95 where that method is under __ARM_NEON in https://gitlab.arm.com/kleidi/kleidiai/-/blob/main/kai/kai_common.h?ref_type=heads#L93 so on 32bit targets with armv6 the compiler with error as there is no implementation of the function.