mpc7448hpc2: Add CONFIG_SYS_I2C_SPEED define

Add standard CONFIG_SYS_I2C_SPEED define for the mpc7448hpc2 so that
it can use the common 'i2c speed' command.  Note that the I2C controller
utilized by the mpc7448hpc2 has a fixed speed and cannot be changed
dynamically.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>

include/configs/mpc7448hpc2.h

@@ -179,6 +179,7 @@
  */
 #define CONFIG_VERSION_VARIABLE		1
 #define CONFIG_TSI108_I2C
+#define CONFIG_SYS_I2C_SPEED		100000	/* I2C speed */
 
 #define CONFIG_SYS_I2C_EEPROM_ADDR		0x50	/* I2C EEPROM page 1 */
 #define CONFIG_SYS_I2C_EEPROM_ADDR_LEN		1	/* Bytes of address */