ARM: dts: aspeed: rainier: Add VGA reserved memory region

The BMC uses reserves the top 16MB of memory for the host to use for VGA
or PCIe communication.

Reviewed-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

@@ -33,6 +33,11 @@
 			no-map;
 			reg = <0xB8000000 0x04000000>; /* 64M */
 		};
+
+		vga_memory: region@bf000000 {
+                        no-map;
+                        reg = <0xbf000000 0x01000000>;  /* 16M */
+                };
 	};
 
 	gpio-keys {