dt-bindings: serial: 8250: spacemit: fix clock property for K3 SoC

dt-bindings: serial: 8250: spacemit: fix clock property for K3 SoC

The UART of SpacemiT K3 SoC has same clock property as K1 generation which
request two clock sources, fix the binding otherwise will get DT check
warnings.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20260304-01-uart-clock-names-v1-1-338483f04a8b@kernel.org
Signed-off-by: Yixun Lan <dlan@kernel.org>