i2c-bfin-twi: Add repeat start feature to avoid break of a bundle of i2c master xfer operation

 - Create a new mode TWI_I2C_MODE_REPEAT.
 - No change to smbus operation.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>