i2c-davinci: Fix timeout handling

Properly set the adapter timeout value in jiffies, and then use that
value in the driver, rather than a hard-coded constant.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Troy Kisky <troy.kisky@boundarydevices.com>
Cc: Kevin Hilman <khilman@mvista.com>