leds: pca955x: Correct I2C Functionality

The driver checks an incorrect flag of functionality of adapter.
When a driver requires i2c_smbus_read_byte_data and
i2c_smbus_write_byte_data, it should check I2C_FUNC_SMBUS_BYTE_DATA
instead I2C_FUNC_I2C.
This patch fixes the problem.

Signed-off-by: Tin Huynh <tnhuynh@apm.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>