ARM: dts: aspeed: rainier: Enable XDMA engine

Fix the VGA reserved memory node, and add the XDMA engine node,
enable it, and point it's memory region to the VGA memory.
Signed-off-by: Eddie James <eajames@linux.ibm.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts

@@ -52,9 +52,10 @@ flash_memory: region@B8000000 {
 		};
 
 		vga_memory: region@bf000000 {
-                        no-map;
-                        reg = <0xbf000000 0x01000000>;  /* 16M */
-                };
+			no-map;
+			compatible = "shared-dma-pool";
+			reg = <0xbf000000 0x01000000>;  /* 16M */
+		};
 	};
 
 	gpio-keys {
@@ -1121,3 +1122,8 @@ flash@0 {
 		spi-max-frequency = <100000000>;
 	};
 };
+
+&xdma {
+	status = "okay";
+	memory-region = <&vga_memory>;
+};