surfaceflinger: remove USE_HWC2

Remove USE_HWC2 and assume it to be true.  Remove all !USE_HWC2
code.

This also fixes a compile error in tests/fakehwc, which never
defines USE_HWC2.

Test: boots taimen and hikey960
Change-Id: Ie6d2fcf884aa6fc715ab0ce19a1e0f7c8acf734c
diff --git a/services/surfaceflinger/RenderArea.h b/services/surfaceflinger/RenderArea.h
index faf1ec6..44b9dc9 100644
--- a/services/surfaceflinger/RenderArea.h
+++ b/services/surfaceflinger/RenderArea.h
@@ -24,10 +24,8 @@
     int getReqHeight() const { return mReqHeight; };
     int getReqWidth() const { return mReqWidth; };
     Transform::orientation_flags getRotationFlags() const { return mRotationFlags; };
-#ifdef USE_HWC2
     virtual bool getWideColorSupport() const = 0;
     virtual android_color_mode_t getActiveColorMode() const = 0;
-#endif
 
     status_t updateDimensions();
 
@@ -37,4 +35,4 @@
     Transform::orientation_flags mRotationFlags;
 };
 
-} // namespace android
\ No newline at end of file
+} // namespace android