dt-bindings: clk: microchip: mpfs: add reset controller support

The "peripheral" devices on PolarFire SoC can be put into reset, so
update the device tree binding to reflect the presence of a reset
controller.

Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20220909123123.2699583-4-conor.dooley@microchip.com