dmaengine: dmatest: exclude compare and fill time during perf report

Dmatest is currently including compare and fill time into the
calculated performance numbers. This does not reflect the HW
capability and the results vary based on the CPU speed instead of
the HW speed.

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>