dt-bindings: aspeed-i2c: Convert txt to yaml format

Convert aspeed i2c to yaml.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Link: https://lore.kernel.org/r/20210603024839.27976-2-jamin_lin@aspeedtech.com


Signed-off-by: Rob Herring <robh@kernel.org>