i2c: busses: i2c-cadence: Fix incorrectly documented 'enum cdns_i2c_slave_mode'

Fixes the following W=1 kernel build warning(s):

 drivers/i2c/busses/i2c-cadence.c:157: warning: expecting prototype for enum cdns_i2c_slave_mode. Prototype was for enum cdns_i2c_slave_state instead
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-cadence.c

@@ -144,7 +144,7 @@ enum cdns_i2c_mode {
 };
 
 /**
- * enum cdns_i2c_slave_mode - Slave state when I2C is operating in slave mode
+ * enum cdns_i2c_slave_state - Slave state when I2C is operating in slave mode
  *
  * @CDNS_I2C_SLAVE_STATE_IDLE: I2C slave idle
  * @CDNS_I2C_SLAVE_STATE_SEND: I2C slave sending data to master