Kernel: Mark PCISerialDevice::detect() as UNMAP_AFTER_INIT

Kernel/Devices/PCISerialDevice.cpp

@@ -10,7 +10,7 @@ namespace Kernel {
 
 static SerialDevice* s_the = nullptr;
 
-void PCISerialDevice::detect()
+UNMAP_AFTER_INIT void PCISerialDevice::detect()
 {
     size_t current_device_minor = 68;
     PCI::enumerate([&](const PCI::Address& address, PCI::ID id) {