staging/ion: condition unmapped heap to supported architectures

Condition ION unmapped heap implementation to architectures that
currently support it. ARM is one of these.

Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>
(cherry picked from commit a52276c2ac562caffc1ba3506e870a88f043e5a8)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
1 file changed