Kernel: Implement DevFileSystem::remove_device

This function cleanly removes the devices from the whole filesystem.

USB devices are now removed from the filesystem as soon as they are
destroyed.

kernel/kernel/USB/HID/HIDDriver.cpp

@@ -78,7 +78,10 @@ namespace Kernel
 	{}
 
 	USBHIDDriver::~USBHIDDriver()
-	{}
+	{
+		if (m_hid_device)
+			DevFileSystem::get().remove_device(m_hid_device);
+	}
 
 	BAN::ErrorOr<void> USBHIDDriver::initialize()
 	{