fix(plat/arm_fpga): increase initrd size

In the comment in the ARM FPGA DT we promise a generous 100 MB initrd,
but actually describe only a size of 20 MB.

As initrds are the most common and easy userland option for the boards,
let's increase the maximum size to the advertised 100 MB, to avoid
unpacking errors when an initrd exceeds the current limit of 20 MB.

Change-Id: If08ba3fabdad27b2c2aff93b18c3f664728b4348
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

fdts/arm_fpga.dts

@@ -28,7 +28,7 @@
 		bootargs = "console=ttyAMA0,38400n8 earlycon";
 		/* Allow to upload a generous 100MB initrd payload. */
 		linux,initrd-start = <0x0 0x84000000>;
-		linux,initrd-end = <0x0 0x85400000>;
+		linux,initrd-end = <0x0 0x8a400000>;
 	};
 
 	/* /cpus node will be added by BL31 at runtime. */