Kernel/Devices: Ensure appropriate locking on the Device map singleton

Devices might be removed and inserted at anytime, so let's ensure we
always do these kind of operations with a good known state of the
HashMap.

The VirtIO code was modified to create devices outside the IRQ handler,
so now it works with the new locking of the devices singleton, but a
better approach might be needed later on.

Kernel/Devices/Device.h

@@ -19,6 +19,7 @@
 #include <AK/HashMap.h>
 #include <Kernel/Devices/AsyncDeviceRequest.h>
 #include <Kernel/FileSystem/File.h>
+#include <Kernel/FileSystem/SysFSComponent.h>
 #include <Kernel/Locking/Mutex.h>
 #include <Kernel/UnixTypes.h>
 
@@ -61,7 +62,7 @@ protected:
     void set_uid(UserID uid) { m_uid = uid; }
     void set_gid(GroupID gid) { m_gid = gid; }
 
-    static HashMap<u32, Device*>& all_devices();
+    static MutexProtected<HashMap<u32, Device*>>& all_devices();
 
 private:
     unsigned m_major { 0 };