dmaengine: fsl-qdma: add MODULE_LICENSE

The newly added driver lacks a MODULE_LICENSE tag, which now produces
a warning:

WARNING: modpost: missing MODULE_LICENSE() in drivers/dma/fsl-qdma.o

Add the license according to the SPDX specifier.

Fixes: 75628c149b0d ("dmaengine: fsl-qdma: Add qDMA controller driver for Layerscape SoCs")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vkoul@kernel.org>