Comment about external PA module boards

variants/diy/v1/variant.h

@@ -44,6 +44,9 @@
 #define RF95_RXEN 14
 #define RF95_TXEN 13
 
+// Set lora.tx_power to 13 for Hydra or other E22 900M30S target due to PA
+#define SX126X_MAX_POWER 22
+
 #ifdef EBYTE_E22
 // Internally the TTGO module hooks the SX126x-DIO2 in to control the TX/RX switch
 // (which is the default for the sx1262interface code)