Kernel: Remove "non-operational" ACPI parser state

If we don't support ACPI, just don't instantiate an ACPI parser.
This is way less confusing than having a special parser class whose
only purpose is to do nothing.

We now search for the RSDP in ACPI::initialize() instead of letting
the parser constructor do it. This allows us to defer the decision
to create a parser until we're sure we can make a useful one.

Kernel/init.cpp

@@ -167,9 +167,6 @@ void init_stage2()
     SyncTask::spawn();
     FinalizerTask::spawn();
 
-    // Sample test to see if the ACPI parser is working...
-    klog() << "ACPI: HPET table @ " << ACPI::Parser::the().find_table("HPET");
-
     PCI::initialize();
 
     if (kernel_command_line().contains("text_debug")) {