libpixelflinger should #define __ARM_HAVE_NEON.

Bug: 18556103
Change-Id: Ife07cf63948f1c248bcde5685cdb6d89c373d988
diff --git a/libpixelflinger/Android.mk b/libpixelflinger/Android.mk
index da9829d..f1bd522 100644
--- a/libpixelflinger/Android.mk
+++ b/libpixelflinger/Android.mk
@@ -36,6 +36,7 @@
 
 ifeq ($(ARCH_ARM_HAVE_NEON),true)
 PIXELFLINGER_SRC_FILES_arm += col32cb16blend_neon.S
+PIXELFLINGER_CFLAGS_arm += -D__ARM_HAVE_NEON
 endif
 
 PIXELFLINGER_SRC_FILES_arm64 := \