[mpp_log]: Add more log helper function

1. Move mpp_log.h to inc for external user.
2. Add mpp_debug.h for mpp internal logging.
3. Fix some warning.
4. Add log level setup function.
5. Check env log_level value in mpp_get_log_level call.

NOTE:
1. mpp internal module should use mpp_debug.h and mpp external user
should use mpp_log.h
2. Use mpp_get_log_level to update mpp_log_level when the env changed.

Change-Id: I90a55a02a72db177533013280dfe111ca3479229
Signed-off-by: Herman Chen <herman.chen@rock-chips.com>

test/mpi_dec_multi_test.c

@@ -21,6 +21,8 @@
 #define MODULE_TAG "mpi_dec_multi_test"
 
 #include <string.h>
+#include <pthread.h>
+
 #include "rk_mpi.h"
 
 #include "mpp_mem.h"
@@ -28,9 +30,7 @@
 #include "mpp_time.h"
 #include "mpp_common.h"
 
-#include "utils.h"
 #include "mpi_dec_utils.h"
-#include <pthread.h>
 
 /* For each instance thread setup */
 typedef struct {