Make getI2CBufferSize constexpr

Compiler hint, can be computed at compile time.

Author: wolfbert

src/SparkFun_External_EEPROM.cpp

@@ -115,7 +115,7 @@ void ExternalEEPROM::disablePollForWriteComplete()
 {
   settings.pollForWriteComplete = false;
 }
-uint16_t ExternalEEPROM::getI2CBufferSize()
+constexpr uint16_t ExternalEEPROM::getI2CBufferSize()
 {
   return I2C_BUFFER_LENGTH_TX;
 }

src/SparkFun_External_EEPROM.h

@@ -117,7 +117,7 @@ class ExternalEEPROM
   uint8_t getPageWriteTime();
   void enablePollForWriteComplete(); //Most EEPROMs all I2C polling of when a write has completed
   void disablePollForWriteComplete();
-  uint16_t getI2CBufferSize(); //Return the size of the TX buffer
+  constexpr uint16_t getI2CBufferSize(); //Return the size of the TX buffer
 
   //Functionality to 'get' and 'put' objects to and from EEPROM.
   template <typename T>