Add I2C_MUX and PCA954x to defconfig

Change-Id: I3d8c1820f4b76ac5067a421ee1dafae53b20350a
diff --git a/debian/defconfig b/debian/defconfig
index 78baac0..c88e38a 100644
--- a/debian/defconfig
+++ b/debian/defconfig
@@ -86,3 +86,5 @@
 CONFIG_SENSORS_INA233=m
 CONFIG_LEDS_KTD202X=y
 CONFIG_USB_USB5744=m
+CONFIG_I2C_MUX=y
+CONFIG_I2C_MUX_PCA954x=m