[POWERPC] Fix mpc52xx serial driver to work for arch/ppc again

The mpc52xx_uart_of_enumerate() function was added when adding 52xx
support to arch/powerpc, but it must not be called for arch/ppc.
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

drivers/serial/mpc52xx_uart.c

@@ -789,7 +789,9 @@ static struct console mpc52xx_console = {
 static int __init
 mpc52xx_console_init(void)
 {
+#if defined(CONFIG_PPC_MERGE)
 	mpc52xx_uart_of_enumerate();
+#endif
 	register_console(&mpc52xx_console);
 	return 0;
 }