serial: sh-sci: fix up serial DMA build.

asm/dmaengine.h no longer exists, update for the shared linux/sh_dma.h
header.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

include/linux/serial_sci.h

@@ -2,9 +2,7 @@
 #define __LINUX_SERIAL_SCI_H
 
 #include <linux/serial_core.h>
-#ifdef CONFIG_SERIAL_SH_SCI_DMA
-#include <asm/dmaengine.h>
-#endif
+#include <linux/sh_dma.h>
 
 /*
  * Generic header for SuperH SCI(F) (used by sh/sh64/h8300 and related parts)