arm: mvebu: i2c come back in defconfig

When the patch "arm: mvebu: Use dw-apb-uart instead of ns16650 as UART
driver" was applied to a git tree and became the commit b24212fb
it wrongly removed the i2c support. This patch reintroduce it.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>