power: Simplify soc_id checks

- Get soc_id in a common util function
 - Return boolean values for the target-specific soc_id checks

Change-Id: I038c435d28855859f36566de7acf881037d070f2

utils.h

@@ -47,4 +47,7 @@ void release_request(int lock_handle);
 void interaction(int duration, int num_args, int opt_list[]);
 int interaction_with_handle(int lock_handle, int duration, int num_args, int opt_list[]);
 int perf_hint_enable(int hint_id, int duration);
+
+int get_soc_id(void);
+
 PropVal perf_get_property(const char* prop, const char* def_val);