freedreno: add the a6xx sources to the Android build

Add the files otherwise things just won't build.
Haven't actually tested it, but it's a small step in the right
direction.

Fixes: de3b34df97 ("freedreno: Add a6xx backend")
Cc: Kristian H. Kristensen <hoegsberg@chromium.org>
Cc: Rob Clark <robdclark@gmail.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>

src/gallium/drivers/freedreno/Android.mk

@@ -31,6 +31,7 @@ LOCAL_SRC_FILES := \
 	$(a3xx_SOURCES)	\
 	$(a4xx_SOURCES) \
 	$(a5xx_SOURCES) \
+	$(a6xx_SOURCES) \
 	$(ir3_SOURCES)
 
 #LOCAL_CFLAGS := \