edtlib: fix possible AttributeError in Property.description

[dottspina]

Attempting to access the property Property.description when Property.spec.description is None would raise:

AttributeError: 'NoneType' object has no attribute 'strip'.

Known affected properties:

• compatible for nodes such as /, /soc, /soc/timer@e000e010, /leds, /pwmleds
• reg for nodes such as /soc/timer@e000e010
• status for nodes such as /soc/timer@e000e010
• gpios for nodes such as /leds/led_0, /buttons/button_0
• pwms for nodes such as /pwmleds/pwm_led_0

This patch checks the PropertySpec.description attribute before calling strip().

Thanks.

-- chris

[dottspina]

It appears zephyr/scripts/dts is still the main repo for these libraries: should I instead propose this PR directly to the zephyr project ?

Thanks.

-- chris

[mbolivar-nordic]

should I instead propose this PR directly to the zephyr project ?

Yes, this is just a mirror. Thank you.