earlycon: add reg-offset to physical address before mapping

It will get the wrong virtual address because port->mapbase is not added
the correct reg-offset yet. We have to update it before earlycon_map()
is called

Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Rob Herring <robh@kernel.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: stable@vger.kernel.org
Fixes: 088da2a17619 ("of: earlycon: Initialize port fields from DT
properties")

drivers/tty/serial/earlycon.c

@@ -245,11 +245,12 @@ int __init of_setup_earlycon(const struct earlycon_id *match,
 	}
 	port->mapbase = addr;
 	port->uartclk = BASE_BAUD * 16;
-	port->membase = earlycon_map(port->mapbase, SZ_4K);
 
 	val = of_get_flat_dt_prop(node, "reg-offset", NULL);
 	if (val)
 		port->mapbase += be32_to_cpu(*val);
+	port->membase = earlycon_map(port->mapbase, SZ_4K);
+
 	val = of_get_flat_dt_prop(node, "reg-shift", NULL);
 	if (val)
 		port->regshift = be32_to_cpu(*val);