gpu: ion: Add heap ids

Add heap ids for ion heaps. Remove unused
system contiguous heap. Fix vmalloc heap name.

Change-Id: I3c3a653a53c8db8b66a7bba2abac0dfe560c407c
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Ronny Schmatzler <schmatzler@googlemail.com>