dm: Avoid accessing seq directly

At present various drivers etc. access the device's 'seq' member directly.
This makes it harder to change the meaning of that member. Change access
to go through a function instead.

The drivers/i2c/lpc32xx_i2c.c file is left unchanged for now.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/mtd/spi/sandbox.c b/drivers/mtd/spi/sandbox.c
index 740bd75..3c01e3b 100644
--- a/drivers/mtd/spi/sandbox.c
+++ b/drivers/mtd/spi/sandbox.c
@@ -131,7 +131,7 @@
 	int ret = 0;
 	int cs = -1;
 
-	debug("%s: bus %d, looking for emul=%p: ", __func__, bus->seq, dev);
+	debug("%s: bus %d, looking for emul=%p: ", __func__, dev_seq(bus), dev);
 	ret = sandbox_spi_get_emul(state, bus, dev, &emul);
 	if (ret) {
 		printf("Error: Unknown chip select for device '%s'\n",
@@ -565,7 +565,7 @@
 			 struct udevice **emulp)
 {
 	struct sandbox_spi_info *info;
-	int busnum = bus->seq;
+	int busnum = dev_seq(bus);
 	int cs = spi_chip_select(slave);
 	int ret;