dt-bindings: reset: add dt binding header for Mediatek MT7621 resets

Add dt binding header for resets lines in Mediatek MT7621 SoCs.

Acked-by: Rob Herring <robh@kernel.org>
Tested-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20220110114930.1406665-2-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>