drivers: dma: Include appropriate header file in dca.c

Includes an appropriate header file dma_v2.h in ioat/dca.c because
functions ioat2_dca_init() and ioat3_dca_init() have their function
declarations in dma_v2.h.

This eliminates the following warning in ioat/dca.c:
drivers/dma/ioat/dca.c:410:22: warning: no previous prototype for ‘ioat2_dca_init’ [-Wmissing-prototypes]
drivers/dma/ioat/dca.c:624:22: warning: no previous prototype for ‘ioat3_dca_init’ [-Wmissing-prototypes]
Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dma/ioat/dca.c

@@ -35,6 +35,7 @@
 
 #include "dma.h"
 #include "registers.h"
+#include "dma_v2.h"
 
 /*
  * Bit 7 of a tag map entry is the "valid" bit, if it is set then bits 0:6