Add getCodingRate() to CustomLR1110 and CustomLR1110Wrapper

LR1110 has codingRate as protected field in LR_common.h, so
getCodingRate() is implemented in CustomLR1110 class directly,
and exposed via CustomLR1110Wrapper override.

This enables dynamic MAX_TEXT_LEN calculation for T1000-E
under JP_STRICT mode.

Author: jirogit

src/helpers/radiolib/CustomLR1110.h

@@ -36,4 +36,8 @@ class CustomLR1110 : public LR1110 {
       bool detected = ((irq & RADIOLIB_LR11X0_IRQ_SYNC_WORD_HEADER_VALID) || (irq & RADIOLIB_LR11X0_IRQ_PREAMBLE_DETECTED));
       return detected;
     }
-};
+
+    uint8_t getCodingRate() const {
+      return this->codingRate + 4;  // RadioLib stores 1-4, return 5-8
+    }
+};

src/helpers/radiolib/CustomLR1110Wrapper.h

@@ -31,4 +31,8 @@ class CustomLR1110Wrapper : public RadioLibWrapper {
   bool getRxBoostedGainMode() const override {
     return ((CustomLR1110 *)_radio)->getRxBoostedGainMode();
   }
+
+  uint8_t getCodingRate() const override {
+    return ((CustomLR1110 *)_radio)->getCodingRate();
+  }
 };