gpu: ion: Don't assume that heaps must be removed

The current check on Ion heaps is too restrictive. It assumes that
all heaps specified with a base address (implying it is a carveout
like heap) must have memory removed with memblock_remove. This is
not a valid assumption. Newer memory managment techniques such
as CMA will not remove memory from the memblock. Ensuring that
memory is properly removed can and should be done elsewhere.
Remove this check entirely.

Change-Id: If2ef1fe2b7f1d3e34c7f48a1a48d2f566d916f93
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>