dt-bindings: spi: amlogic,a1-spifc: add missing power-domains

On the Amlogic A1, the SPI FC controller can require a power-domain to
operate, add it as optional.

Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://msgid.link/r/20240605-topic-amlogic-upstream-bindings-fixes-power-domains-spifc-v1-1-380f29ba4a16@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>