[core] Keep declarations unconditional to fix clang-tidy

component.h is included before defines.h in application.h,
so the #ifdef guards on declarations were evaluated before the
define was visible. Keep declarations always visible (harmless
unused declarations cost nothing) and only guard the definitions.

esphome/core/component.h

@@ -109,9 +109,7 @@ class Component {
 
   float get_actual_setup_priority() const;
 
-#ifdef USE_SETUP_PRIORITY_OVERRIDE
   void set_setup_priority(float priority);
-#endif
 
   /** priority of loop(). higher -> executed earlier
    *
@@ -564,9 +562,8 @@ class WarnIfComponentBlockingGuard {
   Component *component_;
 };
 
-#ifdef USE_SETUP_PRIORITY_OVERRIDE
 // Function to clear setup priority overrides after all components are set up
+// Only has an implementation when USE_SETUP_PRIORITY_OVERRIDE is defined
 void clear_setup_priority_overrides();
-#endif
 
 }  // namespace esphome