staging: android: ion: Drop ion_carveout_allocate definitions

ion_carveout_allocate and ion_carveout_free aren't used outside of the
carveout heap. Get rid of the definitions.

Signed-off-by: Laura Abbott <labbott@redhat.com>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>