udev: rename various validate() -> should_reload() for builtin commands

Previously, true by validate() means several configs are outdated and we
need to reload configs. That's not intuitive for me. Let's rename the
functions.

src/shared/hwdb-util.c

@@ -680,7 +680,7 @@ int hwdb_query(const char *modalias, const char *root) {
         return 0;
 }
 
-bool hwdb_validate(sd_hwdb *hwdb) {
+bool hwdb_should_reload(sd_hwdb *hwdb) {
         bool found = false;
         const char* p;
         struct stat st;

src/shared/hwdb-util.h

@@ -5,6 +5,6 @@
 
 #include "sd-hwdb.h"
 
-bool hwdb_validate(sd_hwdb *hwdb);
+bool hwdb_should_reload(sd_hwdb *hwdb);
 int hwdb_update(const char *root, const char *hwdb_bin_dir, bool strict, bool compat);
 int hwdb_query(const char *modalias, const char *root);