The trace_* family (trace/trace_error/trace_warn/trace_detail, used in the
F/W and init/config paths) was gated behind the compile-time
AQ_CFG_DEBUG_LVL, which is 0, so the dbg_level_/dbg_categories_ runtime
variables were dead and tracing could only be enabled by recompiling.
Decouple trace_base_ from AQ_CFG_DEBUG_LVL so it is always compiled and
gated purely at runtime on dbg_level_/dbg_categories_, make those two
variables writable (no longer const, default level 0 = off), and expose
them as dev.aq.N.debug (verbosity) and dev.aq.N.debug_categories
(subsystem mask) sysctls.
The datapath-heavy AQ_DBG_ENTER/PRINT/DUMP macros and the trace_aq_*_descr
descriptor dumps stay behind AQ_CFG_DEBUG_LVL (still 0), so the per-packet
paths are untouched -- trace_* is only used off the datapath. The two
variables are global (the trace macros reference them directly), so the
per-device sysctls share one backing store, which is fine for a debug
knob.
Validated on AQC107: dev.aq.0.debug defaults to 0 with no trace output;
setting it to 6 emits the F/W init/reset/capabilities traces on the next
F/W operation; setting it back to 0 silences them; traffic unaffected at
line rate, rx_err=0.