sensing: sensor_mgmt: Use kernel heap for allocations

Use the kernel heap instead of the libc heap, improving
security and consistency.

Signed-off-by: Ibrahim Abdalkader <i.abdalkader@gmail.com>

samples/subsys/sensing/simple/prj.conf

@@ -1 +1,2 @@
 CONFIG_LOG=y
+CONFIG_HEAP_MEM_POOL_SIZE=2048

subsys/mgmt/mcumgr/grp/settings_mgmt/Kconfig

@@ -35,7 +35,7 @@ config MCUMGR_GRP_SETTINGS_BUFFER_TYPE_HEAP
 	depends on HEAP_MEM_POOL_SIZE > 0
 	help
 	  Use dynamic heap memory allocation through k_malloc, if there is insufficient heap
-      memory for the allocation then the request will be rejected.
+	  memory for the allocation then the request will be rejected.
 
 endchoice
 

subsys/sensing/sensor_mgmt.c

@@ -342,7 +342,7 @@ int open_sensor(struct sensing_sensor *sensor, struct sensing_connection **conn)
 	}
 
 	/* create connection from sensor to application(client = NULL) */
-	tmp_conn = malloc(sizeof(*tmp_conn));
+	tmp_conn = k_malloc(sizeof(*tmp_conn));
 	if (!tmp_conn) {
 		return -ENOMEM;
 	}
@@ -371,7 +371,7 @@ int close_sensor(struct sensing_connection **conn)
 
 	save_config_and_notify(tmp_conn->source);
 
-	free(*conn);
+	k_free(*conn);
 	*conn = NULL;
 
 	return 0;