Fix efr32-brd4161a-lock-rpc build (#22164)

Fix the conditional compilation in the EFR32 sources to match
their headers. This avoids the following compilation errors:

2022-08-25 13:26:54 INFO    ../../examples/lock-app/efr32/third_party/connectedhomeip/examples/platform/efr32/display/lcd.cpp: In member function 'void SilabsLCD::WriteDemoUI(bool)':
2022-08-25 13:26:54 INFO    ../../examples/lock-app/efr32/third_party/connectedhomeip/examples/platform/efr32/display/lcd.cpp:125:9: error: 'mShowQRCode' was not declared in this scope
2022-08-25 13:26:54 INFO      125 |     if (mShowQRCode)
2022-08-25 13:26:54 INFO          |         ^~~~~~~~~~~
2022-08-25 13:26:54 INFO    At global scope:
2022-08-25 13:26:54 INFO    cc1plus: note: unrecognized command-line option '-Wno-unknown-warning-option' may have been intended to silence earlier diagnostics

2022-08-25 13:27:57 INFO    ../../examples/lock-app/efr32/third_party/connectedhomeip/examples/platform/efr32/BaseApplication.cpp: In static member function 'static void BaseApplication::ButtonHandler(AppEvent*)':
2022-08-25 13:27:57 INFO    ../../examples/lock-app/efr32/third_party/connectedhomeip/examples/platform/efr32/BaseApplication.cpp:396:19: error: 'class SilabsLCD' has no member named 'ToggleQRCode'
2022-08-25 13:27:57 INFO      396 |             slLCD.ToggleQRCode();
2022-08-25 13:27:57 INFO          |                   ^~~~~~~~~~~~
2022-08-25 13:27:57 INFO    At global scope:

examples/platform/efr32/BaseApplication.cpp

@@ -391,7 +391,7 @@ void BaseApplication::ButtonHandler(AppEvent * aEvent)
  CancelFunctionTimer();
  mFunction = kFunction_NoneSelected;
 
-#ifdef DISPLAY_ENABLED
+#ifdef QR_CODE_ENABLED
  // TOGGLE QRCode/LCD demo UI
  slLCD.ToggleQRCode();
 #endif

examples/platform/efr32/display/lcd.cpp

@@ -122,10 +122,12 @@ int SilabsLCD::Update(void)
 
 void SilabsLCD::WriteDemoUI(bool state)
 {
+#ifdef QR_CODE_ENABLED
  if (mShowQRCode)
  {
  mShowQRCode = false;
  }
+#endif
  dState.mainState = state;
  WriteDemoUI();
 }