dt-bindings: arm: fsl: Fix syntax error

Fix the following error by replacing tab indent with spaces.
"
Documentation/devicetree/bindings/arm/fsl.yaml:930:46: [error] syntax error: found character '\t' that cannot start any token (syntax)
"

Fixes: d2bf7abf ("dt-bindings: arm: fsl: Add Emtop SoM & Baseboard")
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>