Minor fixes to airrohr-firmware

[mstv]

• chore(airrohr-firmware.ino): Remove trailing whitespace
• fix(DBG_TXT_PRESSURE): Fixup measurement unit (serial output is in Pa, not in hPa)

before:

Temperature (°C): 23.65
Pressure (hPa): 97658.41
Humidity (%): 64.33

after:

Temperature (°C): 23.65
Pressure (Pa): 97658.41
Humidity (%): 64.33

• fix(loop): Update display after fetching sensors in if (send_now)
• fix(sntp_time_set): Avoid overflow to 0 in order to reliably check for NTP sync, saturate this counter at 255 instead