fsl,fifo-depth have default value 64 in driver(sound/soc/fsl/fsl_esai.c).

fsl,esai-synchronous is flag(bool) type. It doesn't make sense to put flag
type into 'required'.

Fix warning:

arch/arm/boot/dts/nxp/imx/imx6q-sabreauto.dtb: esai@2024000: 'fsl,fifo-depth' is a required property
arch/arm/boot/dts/nxp/imx/imx6q-sabreauto.dtb: esai@2024000: 'fsl,esai-synchronous' is a required property
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20240416-esai_arm_dts_warning-v2-1-879e59c0c3b8@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>