Kernel: Fix lock state corruption in AHCIPORT::start_request

This code was unlocking the lock directly, but the Locker is still
attached, causing the lock to be unlocked an extra time, hence
corrupting the internal lock state.

This is extra confusing though, as complete_current_request() runs
without a lock which also looks like a bug. But that's a task for
another day.

Kernel/Storage/AHCIPort.cpp

@@ -454,15 +454,15 @@ void AHCIPort::start_request(AsyncBlockDeviceRequest& request)
  auto result = prepare_and_set_scatter_list(request);
  if (result.has_value()) {
  dbgln_if(AHCI_DEBUG, "AHCI Port {}: Request failure.", representative_port_index());
- m_lock.unlock();
+ locker.unlock();
  complete_current_request(result.value());
  return;
  }
 
  auto success = access_device(request.request_type(), request.block_index(), request.block_count());
  if (!success) {
  dbgln_if(AHCI_DEBUG, "AHCI Port {}: Request failure.", representative_port_index());
- m_lock.unlock();
+ locker.unlock();
  complete_current_request(AsyncDeviceRequest::Failure);
  return;
  }