Convert CONFIG_SYS_I2C_LEGACY to Kconfig and add CONFIG_[ST]PL_SYS_I2C_LEGACY

First, we convert CONFIG_SYS_I2C_LEGACY to Kconfig.  Next, as you cannot
have SYS_I2C_LEGACY and DM_I2C at the same time, introduce
CONFIG_SPL_SYS_I2C_LEGACY so that we can enable the legacy option only
in SPL.  Finally, for some PowerPC cases we also need
CONFIG_TPL_SYS_I2C_LEGACY support.  Convert all of the existing users to
one or more symbols.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index dd2ed3f..1466f8d 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -47,6 +47,28 @@
 	  device (bus child) info is kept as parent platdata. The interface
 	  is defined in include/i2c.h.
 
+config SYS_I2C_LEGACY
+	bool "Enable legacy I2C subsystem and drivers"
+	depends on !DM_I2C
+	help
+	  Enable the legacy I2C subsystem and drivers.  While this is
+	  deprecated in U-Boot itself, this can be useful in some situations
+	  in SPL or TPL.
+
+config SPL_SYS_I2C_LEGACY
+	bool "Enable legacy I2C subsystem and drivers in SPL"
+	depends on SUPPORT_SPL && !SPL_DM_I2C
+	help
+	  Enable the legacy I2C subsystem and drivers in SPL.  This is useful
+	  in some size constrained situations.
+
+config TPL_SYS_I2C_LEGACY
+	bool "Enable legacy I2C subsystem and drivers in TPL"
+	depends on SUPPORT_TPL && !SPL_DM_I2C
+	help
+	  Enable the legacy I2C subsystem and drivers in TPL.  This is useful
+	  in some size constrained situations.
+
 config I2C_CROS_EC_TUNNEL
 	tristate "Chrome OS EC tunnel I2C bus"
 	depends on CROS_EC