i2c: i2c-bfin-twi: Break dead waiting loop if i2c device misbehaves.

Some fault i2c device may hold the sda/scl line and cause i2c driver
wait in the BUS busy loop. The I2C framework already retry the
transfer loop before timeout. Return -EAGAIN instead of pull BUSBUSY
in the other loop.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>