dm: i2c: Provide an offset length parameter where needed

Rather than assuming that the chip offset length is 1, allow it to be
provided. This allows chips that don't use the default offset length to
be used (at present they are only supported by the command line 'i2c'
command which sets the offset length explicitly).

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
diff --git a/board/avionic-design/common/tamonten-ng.c b/board/avionic-design/common/tamonten-ng.c
index bca9183..1704627 100644
--- a/board/avionic-design/common/tamonten-ng.c
+++ b/board/avionic-design/common/tamonten-ng.c
@@ -55,7 +55,7 @@
 	struct udevice *dev;
 	int ret;
 
-	ret = i2c_get_chip_for_busnum(4, PMU_I2C_ADDRESS, &dev);
+	ret = i2c_get_chip_for_busnum(4, PMU_I2C_ADDRESS, 1, &dev);
 	if (ret) {
 		debug("%s: Cannot find PMIC I2C chip\n", __func__);
 		return;