powerpc/44x: Increase warp SD buffer

Newer revs of the FPGA have a larger SD buffer.
Signed-off-by: Sean MacLennan <smaclennan@pikatech.com>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

arch/powerpc/boot/dts/warp.dts

@@ -146,7 +146,7 @@ fpga@2,2000 {
 
 				fpga@2,4000 {
 					compatible = "pika,fpga-sd";
-					reg = <0x00000002 0x00004000 0x00000A00>;
+					reg = <0x00000002 0x00004000 0x00004000>;
 				};
 
 				nor@0,0 {