dm: i2c: Allow muxes to be enabled for SPL separately

Since I2C muxes are seldom needed in SPL, and the code for this increases
the size somewhat, add a separate option to enable I2C muxes for SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/i2c/Makefile

@@ -7,8 +7,8 @@
 obj-$(CONFIG_DM_I2C) += i2c-uclass.o
 obj-$(CONFIG_DM_I2C_COMPAT) += i2c-uclass-compat.o
 obj-$(CONFIG_DM_I2C_GPIO) += i2c-gpio.o
-obj-$(CONFIG_I2C_CROS_EC_TUNNEL) += cros_ec_tunnel.o
-obj-$(CONFIG_I2C_CROS_EC_LDO) += cros_ec_ldo.o
+obj-$(CONFIG_$(SPL_)I2C_CROS_EC_TUNNEL) += cros_ec_tunnel.o
+obj-$(CONFIG_$(SPL_)I2C_CROS_EC_LDO) += cros_ec_ldo.o
 
 obj-$(CONFIG_SYS_I2C_ADI) += adi_i2c.o
 obj-$(CONFIG_I2C_MV) += mv_i2c.o

drivers/i2c/muxes/Kconfig

@@ -7,6 +7,15 @@ config I2C_MUX
 	  bus select is handled automatically when that bus is accessed,
 	  using a suitable I2C MUX driver.
 
+config SPL_I2C_MUX
+	bool "Support I2C multiplexers on SPL"
+	depends on I2C_MUX
+	help
+	  This enables I2C buses to be multiplexed, so that you can select
+	  one of several buses using some sort of control mechanism. The
+	  bus select is handled automatically when that bus is accessed,
+	  using a suitable I2C MUX driver.
+
 config I2C_ARB_GPIO_CHALLENGE
 	bool "GPIO-based I2C arbitration"
 	depends on I2C_MUX

drivers/i2c/muxes/Makefile

@@ -4,4 +4,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 obj-$(CONFIG_I2C_ARB_GPIO_CHALLENGE) += i2c-arb-gpio-challenge.o
-obj-$(CONFIG_I2C_MUX) += i2c-mux-uclass.o
+obj-$(CONFIG_$(SPL_)I2C_MUX) += i2c-mux-uclass.o