Update i2c_api.h

Added i2c_slave_byte_read() and i2c_slave_byte_write() for devices such as the lpc812, lpc824 and lpc1549 that have separate I2C engines for Master and Slave functions.

Author: Willem23

libraries/mbed/hal/i2c_api.h

@@ -46,6 +46,8 @@ void i2c_slave_mode   (i2c_t *obj, int enable_slave);
 int  i2c_slave_receive(i2c_t *obj);
 int  i2c_slave_read   (i2c_t *obj, char *data, int length);
 int  i2c_slave_write  (i2c_t *obj, const char *data, int length);
+int  i2c_slave_byte_read(i2c_t *obj, int last);
+int  i2c_slave_byte_write(i2c_t *obj, int data);
 void i2c_slave_address(i2c_t *obj, int idx, uint32_t address, uint32_t mask);
 #endif