Fix segmentation faults in benchmark tool

* Fix incorrect calculation of LHS matrix stride value

For kernels that use the LHS matrix stride in their API, namely
`kai_matmul_clamp_f32_f32_f32p8x1biasf32_6x8x4_neon_mla` and
`kai_matmul_clamp_f16_f16_f16p16x1biasf16_6x16x8_neon_mla` kernels, the
LHS stride value was calculated incorrectly by computing in terms of
bits, not bytes.

* Fix insufficient allocation of memory for SME kernels

For SME kernels, such as
`kai_matmul_clamp_f32_f32_f32p16vlx1b_1x16vl_sme2_mla`, the tensor sizes
 are in terms of the streaming SVE vector length. Thus, when running SME
  kernels we must scale the LHS/RHS/DST buffer sizes by the VL
  appropriately.

The segmentation faults were discovered when running with address
sanitizer enabled.

Signed-off-by: Jakub Sujak <jakub.sujak@arm.com>

Reviewed-by: Emil Ohlsson <emil.ohlsson@arm.com>
Approved-by: Emil Ohlsson <emil.ohlsson@arm.com>