ipq40xx: DTS style updates for OpenMesh devices

ipq40xx: DTS style updates for OpenMesh devices

The OpenMesh related files were not updated since a while and the new
coding style requirements weren't integrated. This can cause problems
for new devices when an author uses these files as starting point.

* use SPDX-License-Identifiers instead of full license texts
* drop linux,default-trigger with value default-off for LEDs
* led nodes with label "abc:xyz" should have name "xyz_abc"
* led DT labels for "xyz_abc" should be "led_xyz_abc"
* "m25p80@0" flash node should be renamed to "flash@0"
* drop unnecessary empty lines

Signed-off-by: Sven Eckelmann <sven@narfation.org>
[minor commit title and message adjustments]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>