android: gallium/auxiliary: fix "Unused source files" in tesselator

android: gallium/auxiliary: fix "Unused source files" in tesselator

Avoids the following Android Build System error:

FAILED:
build/make/core/binary.mk:1245: error: external/mesa/src/gallium/auxiliary/Android.mk: libmesa_gallium: Unused source files: tessellator/tessellator.hpp
10:24:30 ckati failed with: exit status 1

Fixes: bd0188f ("gallium/auxiliary: add the microsoft tessellator and a pipe wrapper.")
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Acked-by: Dave Airlie <airlied@redhat.com>