dt-bindings: net: dsa: sja1105: Fix indentation warnings

Some of the lines aren't properly indented, causing yamllint to warn
about them:

    .../nxp,sja1105.yaml:70:17: [warning] wrong indentation: expected 18 but found 16 (indentation)

Use the proper indentation to fix those warnings.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Fixes: 070f5b70 ("dt-bindings: net: dsa: sja1105: add SJA1110 bindings")
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210622113327.3613595-1-thierry.reding@gmail.comSigned-off-by: Rob Herring <robh@kernel.org>