access: pf_control is mandatory

As per both usage and documentation ACCESS_CAN_SEEK,
ACCESS_CAN_FASTSEEK, ACCESS_CAN_PAUSE, ACCESS_CAN_CONTROL_PACE and
ACCESS_GET_PTS_DELAY are mandatory. Thus the pf_control callback is
mandatory.

(Note that STREAM_* maps directly to ACCESS_* here.

include/vlc_access.h

@@ -128,8 +128,7 @@ struct access_t
 static inline int access_vaControl( access_t *p_access, int i_query, va_list args )
 {
     if( !p_access ) return VLC_EGENERIC;
-    return p_access->pf_control ? p_access->pf_control( p_access, i_query, args )
-                                : VLC_EGENERIC;
+    return p_access->pf_control( p_access, i_query, args );
 }
 
 static inline int access_Control( access_t *p_access, int i_query, ... )

src/input/access.c

@@ -91,8 +91,7 @@ access_t *access_New( vlc_object_t *p_obj, input_thread_t *p_parent_input,
     if( p_access->p_module == NULL )
         goto error;
 
-    /* if access has pf_readdir, pf_control is not mandatory */
-    assert( p_access->pf_control || p_access->pf_readdir );
+    assert( p_access->pf_control != NULL );
 
     return p_access;