dt-bindings: i2c: adds two more nxp devices

"nxp,pcf2127" and "nxp,pcf2129" are I2c devices, adds them to the list
of trivial i2c devices.

Signed-off-by: Shaohui Xie <Shaohui.Xie@nxp.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>