dmaengine: add missing MODULE_DESCRIPTION() macros

dmaengine: add missing MODULE_DESCRIPTION() macros

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dma/idxd/idxd.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dma/ti/omap-dma.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dma/dmatest.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dma/ioat/ioatdma.o

Add the missing invocations of the MODULE_DESCRIPTION() macro.

Acked-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240606-md-drivers-dma-v2-1-0770dfdf74dd@quicinc.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>