Everywhere: Switch from (void) to [[maybe_unused]] (#4473)

Problem:
- `(void)` simply casts the expression to void. This is understood to
  indicate that it is ignored, but this is really a compiler trick to
  get the compiler to not generate a warning.

Solution:
- Use the `[[maybe_unused]]` attribute to indicate the value is unused.

Note:
- Functions taking a `(void)` argument list have also been changed to
  `()` because this is not needed and shows up in the same grep
  command.

Kernel/Time/APICTimer.cpp

@@ -165,21 +165,18 @@ void APICTimer::reset_to_default_ticks_per_second()
 {
 }
 
-bool APICTimer::try_to_set_frequency(size_t frequency)
+bool APICTimer::try_to_set_frequency([[maybe_unused]] size_t frequency)
 {
-    (void)frequency;
     return true;
 }
 
-bool APICTimer::is_capable_of_frequency(size_t frequency) const
+bool APICTimer::is_capable_of_frequency([[maybe_unused]] size_t frequency) const
 {
-    (void)frequency;
     return false;
 }
 
-size_t APICTimer::calculate_nearest_possible_frequency(size_t frequency) const
+size_t APICTimer::calculate_nearest_possible_frequency([[maybe_unused]] size_t frequency) const
 {
-    (void)frequency;
     return 0;
 }