gpu: ion: Fix ion client name allocation

The ion client name used for debugging were being
allocated on the stack for user space clients. This
causes the name to be garbled when later printed.

Instead, allocate the name from the heap.

Change-Id: Id299d224192f127197bef2eeb22d881b3a31795c
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>