dt-bindings: spi: nxp-fspi: add imx8ulp support

dt-bindings: spi: nxp-fspi: add imx8ulp support

The flexspi on imx8ulp only has 16 number of LUTs, it is different
with flexspi on other imx SoC which has 32 number of LUTs.

Fixes: ef89fd56bdfc ("arm64: dts: imx8ulp: add flexspi node")
Cc: stable@kernel.org
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20240905094338.1986871-2-haibo.chen@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>