[Blackfin] arch: set default value of DEB_DMA_URGENT to YES to avoid DMA aborting caused by conflict between core and DMA

Signed-off-by: Cliff Cai <cliff.cai@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

arch/blackfin/mach-bf548/Kconfig

@@ -7,7 +7,7 @@ menu "BF548 Specific Configuration"
 config DEB_DMA_URGENT
 	bool "DMA has priority over core for ext. accesses"
 	depends on BF54x
-	default n
+	default y
 	help
 	  Treat any DEB1, DEB2 and DEB3 request as Urgent