firmware: stratix10-svc: Add mutex in stratix10 memory management

firmware: stratix10-svc: Add mutex in stratix10 memory management

Add mutex lock to stratix10_svc_allocate_memory and
stratix10_svc_free_memory for thread safety. This prevents race
conditions and ensures proper synchronization during memory operations.
This is required for parallel communication with the Stratix10 service
channel.

Fixes: 7ca5ce896524f ("firmware: add Intel Stratix10 service layer driver")
Cc: stable@vger.kernel.org
Signed-off-by: Mahesh Rao <mahesh.rao@altera.com>
Reviewed-by: Matthew Gerlach <matthew.gerlach@altera.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>