Kernel: Rename Lock to Mutex

Let's be explicit about what kind of lock this is meant to be.

Kernel/Storage/AHCIPort.h

@@ -11,7 +11,7 @@
 #include <Kernel/Devices/Device.h>
 #include <Kernel/IO.h>
 #include <Kernel/Interrupts/IRQHandler.h>
-#include <Kernel/Lock.h>
+#include <Kernel/Mutex.h>
 #include <Kernel/PhysicalAddress.h>
 #include <Kernel/Random.h>
 #include <Kernel/Sections.h>
@@ -102,7 +102,7 @@ private:
     EntropySource m_entropy_source;
     RefPtr<AsyncBlockDeviceRequest> m_current_request;
     SpinLock<u8> m_hard_lock;
-    Lock m_lock { "AHCIPort" };
+    Mutex m_lock { "AHCIPort" };
 
     mutable bool m_wait_for_completion { false };
     bool m_wait_connect_for_completion { false };