ion: Update the system heap type to MSM_SYSTEM and update sys heap ID

In preparation for restoring the GKI system heap, move the existing
system heap into the vendor heap space, leaving the GKI system heap
ID slot empty. For now, alias allocations targeted at ION_HEAP_SYSTEM to
ION_SYSTEM_HEAP_ID until all clients have migrated. Once that
happens, we can remove the aliasing.

Change-Id: Ib1bd74c2a54ebfdcb14da2b04f237ae1b88db189
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>