fix compatibility with Silicon Labs boards

Author: leonardocavagnis

Adafruit_SSD1306.h

@@ -54,7 +54,7 @@ typedef uint32_t PortMask;
 #elif defined(ARDUINO_ARCH_RTTHREAD)
 #undef HAVE_PORTREG
 #elif (defined(__arm__) || defined(ARDUINO_FEATHER52)) &&                      \
-    !defined(ARDUINO_ARCH_MBED) && !defined(ARDUINO_ARCH_RP2040)
+    !defined(ARDUINO_ARCH_MBED) && !defined(ARDUINO_ARCH_RP2040) && !defined(ARDUINO_SILABS)
 typedef volatile uint32_t PortReg;
 typedef uint32_t PortMask;
 #define HAVE_PORTREG