os/pm: Resolve Build Warnings

This commit resolve the below build warnings:

warning: 'pm_state_name' defined but not used
warning: 'wakeup_src_name' defined but not used
warning: unused variable 'pm_state'
warning: assignment discards 'const' qualifier from pointer target type

os/include/tinyara/pm/pm.h

@@ -183,7 +183,6 @@ enum pm_state_e {
 								 */
 	PM_COUNT,
 };
-static const char *pm_state_name[PM_COUNT] = {"PM_NORMAL", "PM_IDLE", "PM_STANDBY", "PM_SLEEP"};
 
 /* This enumeration provides all power management related wakeup source code. */
 
@@ -198,9 +197,6 @@ typedef enum {
 	PM_WAKEUP_SRC_COUNT,
 } pm_wakeup_reason_code_t;
 
-#ifdef CONFIG_PM_METRICS
-static const char *wakeup_src_name[PM_WAKEUP_SRC_COUNT] = {"UNKNOWN", "BLE", "WIFI", "UART CONSOLE", "UART TTYS2", "GPIO", "HW TIMER"};
-#endif
 /* This structure contain pointers callback functions in the driver.  These
  * callback functions can be used to provide power management information
  * to the driver.

os/pm/pm_metrics.c

@@ -51,6 +51,7 @@ typedef struct pm_metric_s pm_metric_t;
 
 static pm_metric_t *g_pm_metrics;
 static bool g_pm_metrics_running = false;
+static const char *wakeup_src_name[PM_WAKEUP_SRC_COUNT] = {"UNKNOWN", "BLE", "WIFI", "UART CONSOLE", "UART TTYS2", "GPIO", "HW TIMER"};
 
 static void pm_print_metrics(double total_time, int n_domains)
 {
@@ -272,7 +273,7 @@ int pm_metrics(int milliseconds)
 	/* Avoid board sleep during PM Metrics initialization */
 	pm_suspended = pm_suspend(PM_IDLE_DOMAIN);
 	/* Allocate memory for initializing PM Metrics measurements */
-	g_pm_metrics = pm_alloc(1, sizeof(pm_metric_t));
+	g_pm_metrics = (pm_metric_t *)pm_alloc(1, sizeof(pm_metric_t));
 	if (g_pm_metrics == NULL) {
 		set_errno(ENOMEM);
 		pmdbg("Unable to initialize pm_metrics, error = %d\n", get_errno());

os/pm/pm_procfs.c

@@ -148,6 +148,8 @@ static int power_stat(const char *relpath, FAR struct stat *buf);
 #define POWER_LEVEL_3   3
 #define POWER_LEVEL_4   4
 
+static const char *pm_state_name[PM_COUNT] = {"PM_NORMAL", "PM_IDLE", "PM_STANDBY", "PM_SLEEP"};
+
 /****************************************************************************
  * Public Data
  ****************************************************************************/
@@ -230,7 +232,7 @@ static int power_find_dirref(FAR const char *relpath, FAR struct power_dir_s *di
 		}
 		return ERROR;
 	}
-	str = relpath;
+	str = (char *)relpath;
 	dir->domain_id = -1;
 	/* Check relpath has "power" mount point */
 	if (checkStart(POWER, true) == OK) {
@@ -350,7 +352,6 @@ static ssize_t power_read(FAR struct file *filep, FAR char *buffer, size_t bufle
 	size_t totalsize;
 	int domain_id;
 	int last_read;
-	int pm_state;
 	/* Function to copy domain information into buffer */
 	void readprint(const char *format, ...) {
 		size_t copysize;