dt-bindings: phy: cdns,torrent-phy: add reset-names

Add reset-names as a required property.

There are no dts files using torrent phy yet, so it is safe to add a new
required property.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://lore.kernel.org/r/20200918083743.213874-1-tomi.valkeinen@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>