armbian-led-state: avoid binary parameters, other minor cleanups

[paolosabatino]

Description

When a led driver or trigger generates a parameter that contains binary or non-printable characters, armbian-led-state-save.sh stores the value that may contain null, carriage return or other non-textual characters that confuse armbian-led-state-restore.sh. Don't store binary values in such case to prevent functionality breakage.

Also moves the systemd dependency after sysinit.target, which seems to be a more reasonable place rather than timers.target

GitHub issue reference:
Jira reference number AR-2505

How Has This Been Tested?

• Tested on a live system against various led triggers and drivers (USB keyboard, ledtrig_netdev kernel module, tm16xx driver display pseudo-led that creates the offending binary parameter quoted in description)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings