Fix for Int4 per-channel SME GEMM kernel failing with n > 64

In kai_matmul_clamp_f32_qai8dxp1vlx8_qsi4cxp4vlx8_1vlx4vl_sme2_mopa:
 * Fix the offset calculation
 * Fix pointer increments in the matmul

Add new shapes to unit tests, to test n > 64

Resolves: #KLEIDIAI-405, #COMPMID-7918

Signed-off-by: Anitha Raj <anitha.raj@arm.com>

Reviewed-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Reviewed-by: Anitha Raj <anitha.raj@arm.com>
Reviewed-by: Emil Ohlsson <emil.ohlsson@arm.com>
Approved-by: Jakub Sujak <jakub.sujak@arm.com>