SF: Remove DisplayDevice::DisplayType conditionals

DisplayDevice::DisplayType will be removed in a follow-up CL.

Bug: 74619554
Test: Build
Change-Id: I215583ecc9594ce3707642bb840b479aae736c1f
diff --git a/services/surfaceflinger/DisplayDevice.h b/services/surfaceflinger/DisplayDevice.h
index dd69404..960fe8a 100644
--- a/services/surfaceflinger/DisplayDevice.h
+++ b/services/surfaceflinger/DisplayDevice.h
@@ -129,6 +129,7 @@
     uint32_t                getLayerStack() const { return mLayerStack; }
     int32_t                 getDisplayType() const { return mType; }
     bool                    isPrimary() const { return mType == DISPLAY_PRIMARY; }
+    bool                    isVirtual() const { return mType == DISPLAY_VIRTUAL; }
     int32_t                 getHwcDisplayId() const { return mHwcDisplayId; }
     const wp<IBinder>&      getDisplayToken() const { return mDisplayToken; }