dt-bindings: serial: 8250: spacemit: set clocks property as required

dt-bindings: serial: 8250: spacemit: set clocks property as required

In SpacemiT's K1 SoC, the clocks for UART are mandatory needed, so
for DT, both clocks and clock-names property should be set as required.

Fixes: 2c0594f9f062 ("dt-bindings: serial: 8250: support an optional second clock")
Signed-off-by: Yixun Lan <dlan@gentoo.org>
Acked-by: "Rob Herring (Arm)" <robh@kernel.org>
Link: https://lore.kernel.org/r/20250718-01-k1-uart-binding-v1-1-a92e1e14c836@gentoo.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>