properly delete dev object, this commit dissapeared, adding it back.

Author: Wenn0101

libraries/SPI/src/SPI.cpp

@@ -84,7 +84,7 @@ void arduino::MbedSPI::begin() {
 }
 
 void arduino::MbedSPI::end() {
-    if (!dev) {
+    if (dev) {
         delete dev;
     }
 }