Convert CONFIG_SYS_I2C_EARLY_INIT to Kconfig

Convert SYS_I2C_EARLY_INIT to Kconfig, and make it depend on
SPL_SYS_I2C_LEGACY.  Remove the weak implementation as it's either
something that needs to exist for real, or shouldn't be called.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 1466f8d..f4df4ba 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -69,6 +69,13 @@
 	  Enable the legacy I2C subsystem and drivers in TPL.  This is useful
 	  in some size constrained situations.
 
+config SYS_I2C_EARLY_INIT
+	bool "Enable legacy I2C subsystem early in boot"
+	depends on BOARD_EARLY_INIT_F && SPL_SYS_I2C_LEGACY && SYS_I2C_MXC
+	help
+	  Add the function prototype for i2c_early_init_f which is called in
+	  board_early_init_f.
+
 config I2C_CROS_EC_TUNNEL
 	tristate "Chrome OS EC tunnel I2C bus"
 	depends on CROS_EC