boards: silabs: fix boards DTS files coding style issues

Fix board DTS coding style issues to prevent them from spreading when a
new board is introduced and uses an existing DTS as a referance.

Issues addressed from Zephyr devicetree style guidelines [1]:
- Don’t insert empty lines before a deindenting };.
- Insert a single empty line to separate nodes at the same hierarchy
  level.
- status is "okay" by default.
- compatible property comes first in node.
- reg property comes second in node.
- status property comes last in node.
- the rest of the properties within are nodes naturally sorted.
- child nodes are sorted by address or alphabetically if there is no
  address.

No functional change.

Link: https://docs.zephyrproject.org/latest/contribute/style/devicetree.html

 [1]
Signed-off-by: Yishai Jaffe <yishai1999@gmail.com>