i2c: davinci: Allow i2c driver available for keystone platforms

Keystone SOCs uses the same I2C IP as available on DaVinci SOCs.
Update the config so that ARCH_KEYSTONE can use it.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>