habanalabs/gaudi2: replace defines for reserved sob/mob with enums

Following patches are going to add more reserved sync objects and
monitors.
To make the counting of these reserved resources simpler, replace the
existing RESERVED_* defines with enumerations.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>