powerpc: Bump COMMAND_LINE_SIZE to 2048

I've had a report that the current limit is too small for
an automated network based installer. Bump it.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/uapi/asm/setup.h

-#include <asm-generic/setup.h>
+#ifndef _UAPI_ASM_POWERPC_SETUP_H
+#define _UAPI_ASM_POWERPC_SETUP_H
+
+#define COMMAND_LINE_SIZE	2048
+
+#endif /* _UAPI_ASM_POWERPC_SETUP_H */