Revert "ANDROID: staging: android: ion: enable modularizing the ion driver"

This reverts commit f64a8b79.

This is a preparation change for merging android-4.19.110 into
msm-4.19 branch.

Revert ION heap modularization as it is not required on this version of
the kernel.

Change-Id: Ib75e5ac96f533b5612fa43e26ee5402941e84b64
Signed-off-by: Ivaylo Georgiev <irgeorgiev@codeaurora.org>