powerpc: dts: turris1x.dts: Add channel labels for temperature sensor

Channel 0 of SA56004ED chip refers to internal SA56004ED chip sensor (chip
itself is located on the board) and channel 1 of SA56004ED chip refers to
external sensor which is connected to temperature diode of the P2020 CPU.

Fixes: 54c15ec3 ("powerpc: dts: Add DTS file for CZ.NIC Turris 1.x routers")
Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220930123901.10251-1-pali@kernel.org