display: Support compile time QMAA

Support compilation if certain MSM headers are not available
when QMAA is on

Change-Id: I662d7b2244a3a838be348723123b90e418d1351e
diff --git a/config/display-product.mk b/config/display-product.mk
index b673ba7..bfaf88e 100644
--- a/config/display-product.mk
+++ b/config/display-product.mk
@@ -90,6 +90,7 @@
 PRODUCT_PROPERTY_OVERRIDES += \
     vendor.display.enable_null_display=0
 else
+TARGET_IS_HEADLESS := true
 PRODUCT_PROPERTY_OVERRIDES += \
     vendor.display.enable_null_display=1
 endif