px4iofirmware: add PX4IO_PERF define to completely disable perf counters

[dagar]

This saves a paltry 64 bytes of ram, but it seems to be enough to get us out of the immediate bind (#14116).

On the upside it does save a good chunk of flash (nearly 1 kB).

$ make px4_io-v2_default bloaty_compare_master

     VM SIZE    
 -------------- 
  [NEW]     +12    channels_cache.7449
  [NEW]      +8    base_time.7109
  [NEW]      +8    last_mem_time.7465
  [NEW]      +4    brightness.7477
  [NEW]      +4    brightness_counter.7478
  [NEW]      +4    counter.7476
  [NEW]      +4    last_count.7110
  [NEW]      +4    new_channel_count.7087
  [NEW]      +4    new_channel_holdoff.7088
  [NEW]      +4    on_counter.7479
  [NEW]      +1    abort_on_idle.7147
  [NEW]      +1    failsafe.7178
  [NEW]      +1    heartbeat.7471
  [ = ]       0    [Unmapped]
  [ = ]       0    [section .debug_abbrev]
  [ = ]       0    [section .debug_aranges]
  [ = ]       0    [section .debug_frame]
  [ = ]       0    [section .debug_info]
  [ = ]       0    [section .debug_line]
  [ = ]       0    [section .debug_loc]
  [ = ]       0    [section .debug_ranges]
  [ = ]       0    [section .debug_str]
  [ = ]       0    [section .strtab]
  [ = ]       0    [section .symtab]
  [ = ]       0    output_limit_init
  [ = ]       0    ppm
  [DEL]      -1    abort_on_idle.7391
  [DEL]      -1    failsafe.7175
  [DEL]      -1    heartbeat.7529
  -5.7%      -4    [section .bss]
  [DEL]      -4    adc_perf
  [DEL]      -4    brightness.7535
  [DEL]      -4    brightness_counter.7536
  [DEL]      -4    c_gather_dsm
  [DEL]      -4    c_gather_ppm
  [DEL]      -4    c_gather_sbus
  [DEL]      -4    counter.7534
  [DEL]      -4    last_count.7339
  [DEL]      -4    new_channel_count.7316
  [DEL]      -4    new_channel_holdoff.7317
  [DEL]      -4    on_counter.7537
  [DEL]      -4    pc_badidle
  [DEL]      -4    pc_crcerr
  [DEL]      -4    pc_errors
  [DEL]      -4    pc_fe
  [DEL]      -4    pc_idle
  [DEL]      -4    pc_ne
  [DEL]      -4    pc_ore
  [DEL]      -4    pc_regerr
  [DEL]      -4    pc_txns
  -5.9%      -8    adc_init
  [DEL]      -8    base_time.7338
  [DEL]      -8    last_mem_time.7523
  [DEL]     -12    channels_cache.7446
  [DEL]     -22    perf_begin
 -19.4%     -28    controls_init
 -25.8%     -32    adc_measure
 -14.8%     -48    rx_dma_callback
  [DEL]     -50    perf_count
  -5.8%     -60    user_start
 -35.3%     -72    interface_init
  -5.0%     -80    controls_tick
 -40.4%     -84    serial_interrupt
  [DEL]    -196    perf_end
  [DEL]    -216    perf_count_interval
  -1.4%    -952    TOTAL

[dagar]

I'm not even sure when perf counters last worked here as perf_alloc requires pthread_mutex_lock, which isn't even available in the px4_io-v2 build. I suppose it's fine to leave it like this for now and someone can fix it in the future if actually needed.

[dagar]

We should also take a pass to resize the stacks.

CONFIG_IDLETHREAD_STACKSIZE=400
CONFIG_USERMAIN_STACKSIZE=1132

Update: let's review that next. #14129

[julianoes]

Why + 1?

[sfuhrer]

Can confirm that this PR makes enough room on the IO for the convergence mixer. 40 bytes free. Thanks @dagar !