tegra: i2c: Enable new CONFIG_SYS_I2C framework

This enables CONFIG_SYS_I2C on Tegra, updating existing boards and the Tegra
i2c driver to support this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/README b/README
index f00e41b..c67106d 100644
--- a/README
+++ b/README
@@ -1980,6 +1980,11 @@
 		    CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
 		    second bus.
 
+		- drivers/i2c/tegra_i2c.c:
+		 - activate this driver with CONFIG_SYS_I2C_TEGRA
+		 - This driver adds 4 i2c buses with a fix speed from
+		   100000 and the slave addr 0!
+
 		additional defines:
 
 		CONFIG_SYS_NUM_I2C_BUSES