habanalabs: fix DRAM usage accounting on context tear down

The patch fix the DRAM usage accounting by adding a missing update of
the DRAM memory consumption, when a context is being torn down without an
organized release of the allocated memory.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>