devlink: Remove unused extern declaration devlink_port_region_destroy()

devlink_port_region_destroy() is never implemented since
commit 544e7c33 ("net: devlink: Add support for port regions").
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230728132113.32888-1-yuehaibing@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/devlink.h

@@ -1790,8 +1790,6 @@ devlink_port_region_create(struct devlink_port *port,
 			   u32 region_max_snapshots, u64 region_size);
 void devl_region_destroy(struct devlink_region *region);
 void devlink_region_destroy(struct devlink_region *region);
-void devlink_port_region_destroy(struct devlink_region *region);
-
 int devlink_region_snapshot_id_get(struct devlink *devlink, u32 *id);
 void devlink_region_snapshot_id_put(struct devlink *devlink, u32 id);
 int devlink_region_snapshot_create(struct devlink_region *region,