dmaengine: virt-dma: add missing MODULE_DESCRIPTION() macro

With ARCH=loongarch, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/dma/virt-dma.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/virt-dma.c

···
 EXPORT_SYMBOL_GPL(vchan_init);
 
 MODULE_AUTHOR("Russell King");
+MODULE_DESCRIPTION("Virtual DMA channel support for DMAengine");
 MODULE_LICENSE("GPL");