ipq40xx: improve support for Edgecore ECW5211

ipq40xx: improve support for Edgecore ECW5211

This adds several stylistic and functional improvements of the recently
added Edgecore ECW5211, especially:

* Drop the local BDFs as those are already in the upstream under different names
* Add SPDX tag to DTS
* Add label MAC address
* Move LED trigger to DTS
* Remove unnecessary status="okay"
* Disable unused SS USB phy as the USB port only supports USB 2.0
* Make uboot-env partition writable
* Remove qcom,poll_required_dynamic property as the driver does not use it
* Tidy up the device recipe

Fixes: 27cd404feb7e ("ipq40xx: add Edgecore ECW5211 support")
Signed-off-by: Sungbo Eo <mans0n@gorani.run>
Acked-by: Robert Marko <robert.marko@sartura.hr>