etnaviv: update Android build files

etnaviv no longer builds on Android, fix this.

Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3447>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3447>
diff --git a/Android.mk b/Android.mk
index ef496c1..59d345b 100644
--- a/Android.mk
+++ b/Android.mk
@@ -97,6 +97,7 @@
 
 # add subdirectories
 SUBDIRS := \
+	src/etnaviv \
 	src/freedreno \
 	src/gbm \
 	src/loader \