update spi test task for PL PCDU

mission/devices/max1227.h

@@ -58,7 +58,7 @@ void prepareExternallyClockedSingleChannelRead(uint8_t* spiBuf, uint8_t channel,
  * If there is a wakeup delay, there needs to be a 65 us delay between sending
  * the first byte (first conversion byte) the the rest of the SPI buffer.
  * @param spiBuf
- * @param n
+ * @param n Channel number. Example: If the ADC has 6 channels, n will be 5
  * @param sz
  */
 void prepareExternallyClockedRead0ToN(uint8_t* spiBuf, uint8_t n, size_t& sz);