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/CPCI405.h b/include/configs/CPCI405.h
index d131aea..3e7020d 100644
--- a/include/configs/CPCI405.h
+++ b/include/configs/CPCI405.h
@@ -256,6 +256,7 @@
  * I2C EEPROM (CAT24WC08) for environment
  */
 #define CONFIG_HARD_I2C			/* I2c with hardware support */
+#define CONFIG_PPC4XX_I2C		/* use PPC4xx driver		*/
 #define CONFIG_SYS_I2C_SPEED		400000	/* I2C speed and slave address */
 #define CONFIG_SYS_I2C_SLAVE		0x7F