Use SPI library for Teensy LC

With this commit no direct register access to SPI hardware should be done anymore for Teensy LC. This is done in the same way as for Teensy 4. Additionally the USE_TEENSY4_SPI define was renamed to USE_SPI_LIB as it is now used for not only Teensy 4.

utility/Sd2Card.cpp

 }
 /** SPI send multiple bytes */
 
-#elif defined(__IMXRT1052__)  || defined(__IMXRT1062__)
- #define USE_TEENSY4_SPI
+#elif defined(__IMXRT1052__)  || defined(__IMXRT1062__) || defined(__MKL26Z64__)
+ #define USE_SPI_LIB
  
  static void spiInit(uint8_t spiRate) {
   switch (spiRate) {
+#ifdef __MKL26Z64__
+    // the top 2 speeds are set to 24 MHz, for the SD library defaults
+    case 0:  settings = SPISettings(24000000, MSBFIRST, SPI_MODE0); break;
+#else
     // the top 2 speeds are set to 24 MHz, for the SD library defaults
     case 0:  settings = SPISettings(25200000, MSBFIRST, SPI_MODE0); break;
+#endif
     case 1:  settings = SPISettings(24000000, MSBFIRST, SPI_MODE0); break;
     case 2:  settings = SPISettings(8000000, MSBFIRST, SPI_MODE0); break;
     case 3:  settings = SPISettings(4000000, MSBFIRST, SPI_MODE0); break;
 #if defined(USE_TEENSY3_SPI)
   spiBegin();
   spiInit(6);
-#elif defined(USE_TEENSY4_SPI)
+#elif defined(USE_SPI_LIB)
   spiInit(6);
   pinMode(SS_PIN, OUTPUT);
   digitalWrite(SS_PIN, HIGH); // disable any SPI device using hardware SS pin  
   if (!waitStartBlock()) {
     goto fail;
   }
-#if defined(USE_TEENSY3_SPI) | defined(USE_TEENSY4_SPI)
+#if defined(USE_TEENSY3_SPI) | defined(USE_SPI_LIB)
   spiRec(dst, 512);
   spiRecIgnore(2);
 #else  // OPTIMIZE_HARDWARE_SPI
  * false, is returned for an invalid value of \a sckRateID.
  */
 uint8_t Sd2Card::setSckRate(uint8_t sckRateID) {
-#if defined(USE_TEENSY3_SPI) || defined(USE_TEENSY4_SPI)
+#if defined(USE_TEENSY3_SPI) || defined(USE_SPI_LIB)
   spiInit(sckRateID);
   return true;
 #else
 //------------------------------------------------------------------------------
 // send one block of data for write block or write multiple blocks
 uint8_t Sd2Card::writeData(uint8_t token, const uint8_t* src) {
-#if defined(OPTIMIZE_HARDWARE_SPI) && !defined(USE_TEENSY4_SPI)
+#if defined(OPTIMIZE_HARDWARE_SPI) && !defined(USE_SPI_LIB)
 
   // send data - optimized loop
   SPDR = token;