log: add missing experimental tag

When rte_log_register_type_and_pick_level() has been introduced, it has
been correctly added to the EXPERIMENTAL section of the eal map and the
symbol itself has been marked at its definition.

However, the declaration of this symbol in rte_log.h is missing the
__rte_experimental tag.
Because of this, a user can try to call this symbol without being aware
this is an experimental api (neither compilation nor link warning).

Fixes: b22e77c026 ("eal: register log type and pick level from args")
Cc: stable@dpdk.org

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>

lib/librte_eal/common/include/rte_log.h

@@ -24,6 +24,7 @@ extern "C" {
 
 #include <rte_common.h>
 #include <rte_config.h>
+#include <rte_compat.h>
 
 struct rte_log_dynamic_type;
 
@@ -226,6 +227,7 @@ int rte_log_register(const char *name);
  *    - >=0: the newly registered log type
  *    - <0: rte_log_register() error value
  */
+__rte_experimental
 int rte_log_register_type_and_pick_level(const char *name, uint32_t level_def);
 
 /**