ARM: dts: imx6ul-kontron-n6x1x-s: Remove an obsolete comment and fix indentation

The ECSPI1 is not used for a FRAM chip, so remove the comment.
While at it, also change some whitespaces to tabs to comply with the
indentation style of the rest of the file.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>