neta device generates kernel panic

[Andrei Martin]

Hello,

While trying to run the FreeBSD on EspressoBin (arm64) a kernel panic
appeared in the neta device.
The following function call[1] was the one generating this behaviour. It
says that the SC mutex
is not owned. My solution was to add the lock/unlock operations, as follows:
*mvneta_sc_lock(sc);*
*mvneta_clear_mib(sc);*
*mvneta_sc_unlock(sc);*

*and it works fine.*

*Also, reading the patch[2], found that `mvneta_clear_mib` does some new
operations (counter_pdfc = counter_pofc = counter_watchdog = 0) than just
clearing MIB counter registers. I do not know if it was intended but it's
worth mentioning.*

[1]
https://github.com/freebsd/freebsd-src/blob/main/sys/dev/neta/if_mvneta.c#L1193
[2]
https://github.com/freebsd/freebsd-src/commit/caf552a607191ffc798e3edb697ae99d5b15711a

Andrei