powerpc: Bump BOOT_COMMAND_LINE_SIZE to 2048

Bump the boot wrapper BOOT_COMMAND_LINE_SIZE to match the
kernel.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/boot/ops.h

@@ -15,7 +15,7 @@
 #include "types.h"
 #include "string.h"
 
-#define	BOOT_COMMAND_LINE_SIZE	512
+#define	BOOT_COMMAND_LINE_SIZE	2048
 #define	MAX_PATH_LEN		256
 #define	MAX_PROP_LEN		256 /* What should this be? */