powercap: DTPM: dtpm_node_callback[] can be static

drivers/powercap/dtpm.c:525:22: warning: symbol 'dtpm_node_callback' was not declared. Should it be static?

Fixes: 3759ec6 ("powercap/drivers/dtpm: Add hierarchy creation")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: kernel test robot <lkp@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: intel-lab-lkp

drivers/powercap/dtpm.c

@@ -470,7 +470,7 @@ static struct dtpm *dtpm_setup_dt(const struct dtpm_node *hierarchy,
 
 typedef struct dtpm * (*dtpm_node_callback_t)(const struct dtpm_node *, struct dtpm *);
 
-dtpm_node_callback_t dtpm_node_callback[] = {
+static dtpm_node_callback_t dtpm_node_callback[] = {
 	[DTPM_NODE_VIRTUAL] = dtpm_setup_virtual,
 	[DTPM_NODE_DT] = dtpm_setup_dt,
 };