gateware/icE1usb: Use custom I2C core by default rather than SB_I2C

SB_I2C is apparently just a pain to use and buggy and such, so
use our custom one.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Change-Id: I1596ccbf03dd4450f519fe9b54a7fece125a7fbc
diff --git a/gateware/icE1usb/rtl/top.v b/gateware/icE1usb/rtl/top.v
index 7762fb0..a2b8979 100644
--- a/gateware/icE1usb/rtl/top.v
+++ b/gateware/icE1usb/rtl/top.v
@@ -12,8 +12,8 @@
 `default_nettype none
 
 // `define WITH_SINGLE_CHANNEL
-`define WITH_SB_I2C
-// `define WITH_CUSTOM_I2C
+// `define WITH_SB_I2C
+`define WITH_CUSTOM_I2C
 
 module top (
 	// E1 PHY