ion: update idr to avoid deprecated apis

Use idr_alloc instead if idr_pre_get/idr_get_new_above, and
remove idr_remove_all.

Change-Id: I675b789879549bd3767ed3ef2016cf108eb622d2
Signed-off-by: Colin Cross <ccross@android.com>
Git-commit: acd77fc7d05a80e7ae39e64e1a3948487e2255ff
Git-repo: https://android.googlesource.com/kernel/common


Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>