vulkan: apply MUL_MAT_ID subgroup optimization to non-coopmat devices (llama/15524)

vulkan: apply MUL_MAT_ID subgroup optimization to non-coopmat devices (llama/15524)

* vulkan: use subgroup function for mul_mat_id shader even without coopmat

* vulkan: fix compile warnings

* vulkan: properly check for subgroup size control and require full subgroups for subgroup mul_mat_id

* vulkan: disable subgroup mul_mat_id on devices with subgroups < 16