Kernel/aarch64: Add {panic,dbgln}_without_mmu

And use it the code that will be part of the early boot process.

The PANIC macro and dbgln functions cannot be used as it accesses global
variables, which in the early boot process do not work, since the MMU is
not yet enabled.

Kernel/Arch/aarch64/Processor.cpp

@@ -36,7 +36,7 @@ void Processor::install(u32 cpu)
     m_physical_address_bit_width = detect_physical_address_bit_width();
     m_virtual_address_bit_width = detect_virtual_address_bit_width();
 
-    initialize_exceptions(cpu);
+    initialize_exceptions();
 
     g_current_processor = this;
 }