Current HBL branch misses sysfs path

Router unable to generate password (/etc/sentinel/mailpass) on version 5.15.59 due to error in mox-otp

sentinel-certgen mailpass
sysfs API error: Could not find MOX sign file
crypto-wrapper: error: Failed to run command 'mox-otp sign /tmp/crypto_wrapper_root/temp_fciNlC'
[2022-08-10 14:35:14] ERROR [certgen.process_auth:250] Auth error: Server responded with message: Bad signature format: 
[2022-08-10 14:35:14] WARNING [certgen.start:335] Sleeping for 12 seconds before retry (try number 2)
sysfs API error: Could not find MOX sign file
crypto-wrapper: error: Failed to run command 'mox-otp sign /tmp/crypto_wrapper_root/temp_EekBHb'
[2022-08-10 14:35:27] ERROR [certgen.process_auth:250] Auth error: Server responded with message: Bad signature format: 
[2022-08-10 14:35:27] WARNING [certgen.start:335] Sleeping for 12 seconds before retry (try number 3)
[2022-08-10 14:35:39] ERROR [certgen.process_get:204] Get fail: Server responded with message: You hit the rate limit
[2022-08-10 14:35:39] ERROR [certgen.start:330] Max tries (3) have been reached, exiting

However, the mox-otp is merely pointing to missing path in sysfs

foot@turris:/ uname -a
Linux turris 5.15.59 #0 SMP Tue Aug 9 23:38:13 2022 aarch64 GNU/Linux
root@turris:/sys/firmware/turris-mox-rwtm# [ -f /sys/firmware/turris-mox-rwtm/mox_do_sign ] ; echo $?
1

Found by @jhoracek

cheers