i2c: Move PPC4xx I2C driver into drivers/i2c directory

This patch moves the PPC4xx specific I2C device driver into the I2C
drivers directory. All 4xx config headers are updated to include this
driver.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/include/configs/zeus.h b/include/configs/zeus.h
index 1a77c71..3b2aede 100644
--- a/include/configs/zeus.h
+++ b/include/configs/zeus.h
@@ -167,6 +167,7 @@
  *----------------------------------------------------------------------*/
 #define CONFIG_HARD_I2C		1		/* I2C with hardware support	*/
 #undef	CONFIG_SOFT_I2C				/* I2C bit-banged		*/
+#define CONFIG_PPC4XX_I2C		/* use PPC4xx driver		*/
 #define CONFIG_SYS_I2C_SPEED		400000		/* I2C speed and slave address	*/
 #define CONFIG_SYS_I2C_SLAVE		0x7F