[KL25Z] Fix I2C issue related to the silicon errata.

Makes a difference when running the I2C EEPROM test at 400KHz, which has a 100%
success rate after this change.

Author: Bogdan Marinescu

libraries/mbed/targets/hal/TARGET_Freescale/TARGET_KL25Z/i2c_api.c

@@ -89,10 +89,18 @@ void i2c_init(i2c_t *obj, PinName sda, PinName scl) {
 }
 
 int i2c_start(i2c_t *obj) {
+    uint8_t temp;
+    volatile int i;
     // if we are in the middle of a transaction
     // activate the repeat_start flag
     if (obj->i2c->S & I2C_S_BUSY_MASK) {
+        // KL25Z errata sheet: repeat start cannot be generated if the
+        // I2Cx_F[MULT] field is set to a non-zero value
+        temp = obj->i2c->F >> 6;
+        obj->i2c->F &= 0x3F;
         obj->i2c->C1 |= 0x04;
+        for (i = 0; i < 100; i ++) __NOP();
+        obj->i2c->F |= temp << 6;
     } else {
         obj->i2c->C1 |= I2C_C1_MST_MASK;
         obj->i2c->C1 |= I2C_C1_TX_MASK;