habanalabs: increment ctx ref from within a cs allocation

A CS must increment the relevant context reference count.
We want to increment the reference inside the CS allocation function
as opposed for today where we increment it outside.
This is logical since we want to avoid explicitly incrementing
the context every time we call the CS allocate function.

Signed-off-by: Ofir Bitton <obitton@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>