fix bridge device section confusion

[pony1k]

Bridge ports are added to the first device section, which may be the wrong one. This changes the behaviour follwing @ilario s suggestion. Now, the first device section that has type bridge and the name br-lan will be used.
After reading the /bin/config_generate script in OpenWrt base-files I am confident that there will always be such a device section on first boot.

fixes #1060

[codecov-commenter]

Codecov Report

Merging #1061 (96590e9) into master (4c51c7e) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 96590e9 differs from pull request most recent head 0bf768e. Consider uploading reports for the commit 0bf768e to get more accurate results

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@@            Coverage Diff             @@
##           master    #1061      +/-   ##
==========================================
+ Coverage   79.67%   79.69%   +0.01%     
==========================================
  Files          53       53              
  Lines        4542     4550       +8     
==========================================
+ Hits         3619     3626       +7     
- Misses        923      924       +1     

Files	Coverage Δ
...s/lime-system/files/usr/lib/lua/lime/proto/lan.lua	80.00% <100.00%> (+3.40%)	⬆️

... and 1 file with indirect coverage changes

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[ilario]

Wow this looks veeerrrry nice!!!!!

And it also solves, in a more elegant way, the problem patched in 6b72b3b

Did you test on OpenWrt 22.03 also?

@spiccinini @G10h4ck check this out

[G10h4ck]

Seems good to me, thanks @pony1k

[pony1k]

I tested it on

• fritzbox 4020, OpenWrt 23.05.0, non-dsa
• fritzbox 4040, OpenWrt 22.03.5, non-dsa
• TP-Link Archer C6 v3, OpenWrt 22.03.5, dsa

By tested I mean I removed all ports from the bridge device section and see if lime-config brings them back. For me is fine to be merged.