Extend support for signed 4-bit integer inputs in kai_rhs_pack_nxk_qsi4cxps1s0_qsu4cxs1s0_neon

Signed-off-by: Evie Wright <evie.wright@arm.com>

Reviewed-by: Felix Johnny Thomasmathibalan <felixjohnny.thomasmathibalan@arm.com>
Reviewed-by: Anton Bondarenko <anton.bondarenko@arm.com>
Approved-by: Felix Johnny Thomasmathibalan <felixjohnny.thomasmathibalan@arm.com>