WIZNET5K.regs() hardcodes 4 sockets instead of using _WIZCHIP_SOCK_NUM_

[DoubleVee73]

The regs() debug method on network.WIZNET5K dumps per-socket registers
using a hardcoded loop bound of 4. This is within the network_wiznet5k.c file in micropython/extmod line 820.

for (int sn = 0; sn < 4; ++sn)

On a W5500 (8 hardware sockets), this means regs() never shows
sockets 4-7. The function already has access to WIZCHIP_SOCK_NUM
which is used correctly elsewhere for this purpose, just not in this loop.

Fix is a one-line change:

for (int sn = 0; sn < _WIZCHIP_SOCK_NUM_; ++sn)

I found this while debugging a socket-exhaustion issue on a W5500.
The register dump looked incomplete compared to what I could see
reading the chip directly over SPI, which is what led me here.

[Josverl]

Thanks for sharing @DoubleVee73.

Do you plan to submit a PR with this fix ?
I do not have the hardware, so I can't verify myself if a PR would even work.

[DoubleVee73]

I don't know how a PR works - but wanted to share in case one of the mods wanted to make this change to the codebase.

So many people have helped me on here so I just wanted to potentially help others - admittedly in a tiny way 😀