accel/habanalabs: fix mem leak in capture user mappings

This commit fixes a memory leak caused when clearing the user_mappings
info when a new context is opened immediately after user_mapping is
captured and a hard reset is performed.

Signed-off-by: Moti Haimovski <mhaimovski@habana.ai>
Reviewed-by: Dani Liberman <dliberman@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>