ARM: dts: aspeed: quanta-q71: Enable p2a node

Enable the aspeed-p2a-ctrl node and configure with memory-region to
enable mmap access.

Signed-off-by: Patrick Venture <[e-mail]>
Signed-off-by: Joel Stanley <[e-mail]>

arch/arm/boot/dts/aspeed-bmc-quanta-q71l.dts

···
 			&pinctrl_ddcclk_default &pinctrl_ddcdat_default>;
 };
 
+&p2a {
+	status = "okay";
+	memory-region = <&vga_memory>;
+};
+
 &ibt {
 	status = "okay";
 };