feat(spi): add transfer api with tx and rx buffer

[fpistm]

Fixes #2205

For ref: arduino/ArduinoCore-API#189

Tested with SdFat patched with:

index 8b7da94..296a752 100644
@@ -44,9 +44,13 @@ void SdSpiArduinoDriver::end() { m_spi->end(); }
 uint8_t SdSpiArduinoDriver::receive() { return m_spi->transfer(0XFF); }
 //------------------------------------------------------------------------------
 uint8_t SdSpiArduinoDriver::receive(uint8_t* buf, size_t count) {
+#if defined(STM32_CORE_VERSION) && STM32_CORE_VERSION > 0x02070000
+  m_spi->transfer(NULL, buf, count);
+#else
   // Must send 0XFF - SD looks at send data for command.
   memset(buf, 0XFF, count);
   m_spi->transfer(buf, count);
+#endif
   return 0;
 }
 //------------------------------------------------------------------------------
@@ -57,9 +61,17 @@ void SdSpiArduinoDriver::send(const uint8_t* buf, size_t count) {
   if (count > 512) {
     return;
   }
+#if defined(STM32_CORE_VERSION)
+#if STM32_CORE_VERSION > 0x02070000
+  m_spi->transfer(buf, NULL, count);
+#elif STM32_CORE_VERSION == 0x02070000
+  #error "STM32 core version 2.7.0 is not compatible due to SPI API changes."
+#endif
+#else
   // Not easy to avoid receive so use tmp RX buffer.
   uint8_t rxBuf[512];
   // Discard const - STM32 not const correct.
   m_spi->transfer(const_cast<uint8_t*>(buf), rxBuf, count);
+#endif
 }
 #endif  // defined(SD_USE_CUSTOM_SPI) && defined(STM32_CORE_VERSION)

[fpistm]

PR is now ready. Thanks @greiman.

Results of bench sketch:

-### 2.6.0
-Sketch uses 41400 bytes (3%) of program storage space. Maximum is 1048576 bytes.
-Global variables use 3296 bytes (3%) of dynamic memory, leaving 95008 bytes for local variables. Maximum is 98304 bytes.
+### 2.7.1
+Sketch uses 40224 bytes (3%) of program storage space. Maximum is 1048576 bytes.
+Global variables use 3248 bytes (3%) of dynamic memory, leaving 95056 bytes for local variables. Maximum is 98304 bytes.
 
-FreeStack: 94912
+FreeStack: 94960
 Type is FAT16
 Card size: 1.98 GB (GB = 1E9 bytes)
 
@@ -20,15 +20,15 @@
 write speed and latency
 speed,max,min,avg
 KB/Sec,usec,usec,usec
-1126.13,154491,406,453
-1089.56,154378,406,468
+1138.69,154066,401,448
+1100.11,155705,401,463
 
 Starting read test, please wait.
 
 read speed and latency
 speed,max,min,avg
 KB/Sec,usec,usec,usec
-1143.64,458,444,445
-1143.90,457,445,445
+1222.79,428,416,417
+1222.49,428,416,417
 
 Done