accel/ivpu: Don't allocate preemption buffers when MIP is disabled

Do not allocate preemption buffers when Mid Inference Preemption (MIP)
is disabled through test mode.

Rename IVPU_TEST_MODE_PREEMPTION_DISABLE to IVPU_TEST_MODE_MIP_DISABLE
to better describe that this test mode only disables MIP - job level
preemption will still occur.

Signed-off-by: Karol Wachowski <karol.wachowski@intel.com>
Reviewed-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241017145817.121590-9-jacek.lawrynowicz@linux.intel.com