dt-bindings: clock: imx: Fix e-mail address

The freescale.com domain is gone for quite some time.

Use the nxp.com domain instead.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20200701005346.1008-1-festevam@gmail.com
Signed-off-by: Rob Herring <robh@kernel.org>