phy: zynqmp: Store instance instead of type

The phy "type" is just the combination of protocol and instance, and is
never used apart from that. Store the instance directly, instead of
converting to a type first. No functional change intended.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Link: https://lore.kernel.org/r/20240628205540.3098010-3-sean.anderson@linux.dev


Signed-off-by: Vinod Koul <vkoul@kernel.org>