[13.4-stable] pkg/debug: fix COM port detection

[christoph-zededa]

Description

Based on #5876

Newer kernels no longer expose /sys/class/tty//device/resources. Switch to reading port and IRQ directly from the per-tty sysfs files /sys/class/tty//port and /sys/class/tty/*/irq.

On x86_64, a port value of 0x0 indicates no hardware is present and the entry is skipped. The IO port range is computed as base to base+7 to match the standard 8-byte UART register window.

Qemu tests:
Effect on EVE master:
4 COM ports are detected, instead of 0

Effect on EVE 14.5:
4 COM ports are detected, instead of 1
This is because the serial port connected via PCI was detected, but not the ones via uart8250.

[debug] root@linuxkit-525400123456:~$ ls -l /sys/class/tty/ | grep ttyS
lrwxrwxrwx    1 root     root             0 Apr 28 10:14 ttyS0 -> ../../devices/pnp0/00:03/tty/ttyS0
lrwxrwxrwx    1 root     root             0 Apr 28 10:14 ttyS1 -> ../../devices/platform/serial8250/tty/ttyS1
lrwxrwxrwx    1 root     root             0 Apr 28 10:14 ttyS2 -> ../../devices/platform/serial8250/tty/ttyS2
lrwxrwxrwx    1 root     root             0 Apr 28 10:14 ttyS3 -> ../../devices/platform/serial8250/tty/ttyS3

How to test and validate this PR

Run spec.sh and check that all COM ports are printed.

Changelog notes

Fix COM port detection in spec.sh

Also, to the PRs that should be backported into any stable branch, please
add a label stable.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 27.29%. Comparing base (8077a3d) to head (6a984c4).
⚠️ Report is 186 commits behind head on 13.4-stable.

Additional details and impacted files

@@               Coverage Diff               @@
##           13.4-stable    #5891      +/-   ##
===============================================
+ Coverage        24.78%   27.29%   +2.51%     
===============================================
  Files                8        8              
  Lines             1138      828     -310     
===============================================
- Hits               282      226      -56     
+ Misses             788      534     -254     
  Partials            68       68              

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