Convert CONFIG_SYS_I2C_SPEED et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_I2C_SPEED
   CONFIG_SYS_I2C_SLAVE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/compulab/imx8mm-cl-iot-gate/spl.c b/board/compulab/imx8mm-cl-iot-gate/spl.c
index 8f59245..2dc62d6 100644
--- a/board/compulab/imx8mm-cl-iot-gate/spl.c
+++ b/board/compulab/imx8mm-cl-iot-gate/spl.c
@@ -176,7 +176,7 @@
 
 	enable_tzc380();
 
-	setup_i2c(1, CONFIG_SYS_I2C_SPEED, 0x7f, &i2c_pad_info1);
+	setup_i2c(1, 100000, 0x7f, &i2c_pad_info1);
 
 	power_init_board();