cpu-set-util: introduce config_parse_cpu_set()

Then, make parse_cpu_set() as a tiny wrapper of it.

Note, previously when an invalid CPU range, e.g. "3-0", is specified,
we ignore the range but allocate an empty set. But, with this commit,
now the conf parser simply ignore it without no side effect.
This potentially changes behavior of a system with such invalid setting,
but the change should be favorable for consistency with other parsers.

src/udev/net/link-config.c

@@ -1371,15 +1371,8 @@ int config_parse_rps_cpu_mask(
         CPUSet *mask = ASSERT_PTR(data);
         int r;
 
-        assert(filename);
-        assert(lvalue);
         assert(rvalue);
 
-        if (isempty(rvalue)) {
-                cpu_set_done(mask);
-                return 0;
-        }
-
         if (streq(rvalue, "disable")) {
                 _cleanup_(cpu_set_done) CPUSet c = {};
 
@@ -1403,11 +1396,7 @@ int config_parse_rps_cpu_mask(
                 return cpu_set_done_and_replace(*mask, c);
         }
 
-        r = parse_cpu_set_extend(rvalue, mask, /* warn= */ true, unit, filename, line, lvalue);
-        if (r < 0)
-                return 0;
-
-        return 0;
+        return config_parse_cpu_set(unit, filename, line, section, section_line, lvalue, ltype, rvalue, data, userdata);
 }
 
 static const char* const mac_address_policy_table[_MAC_ADDRESS_POLICY_MAX] = {