ARM: keystone: Enable DM_I2C by default

Enable by default DM_I2C for all Texas Instruments Keystone 2 based
evms.

Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Heiko Schocher <hs@denx.de>