dmaengine: dmatest: use strscpy to replace strlcpy

The strlcpy should not be used because it doesn't limit the source
length. Preferred is strscpy.

Signed-off-by: XueBing Chen <chenxuebing@jari.cn>
Link: https://lore.kernel.org/r/12e4cf06.a35.180fa748c29.Coremail.chenxuebing@jari.cn


Signed-off-by: Vinod Koul <vkoul@kernel.org>