dmaengine: dmatest: Remove spaces before tabs

Scripts/checkpath.pl says "please, no space before tabs".
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/d863916120d043e3f9dd2f2670238c34f68f7d5f.1654702886.git.geert+renesas@glider.beSigned-off-by: Vinod Koul <vkoul@kernel.org>