Kernel/AHCI: Dont assume ports start at 0

This fixes a bug that occurs when the controller's ports are not
(internally) numbered sequentially.
This is done by checking the bits set in PI.
This bug was found on bare-metal, on a laptop with 1 Port that
was reported as port 4.

Kernel/Storage/AHCIController.cpp

@@ -181,12 +181,18 @@ RefPtr<StorageDevice> AHCIController::device_by_port(u32 port_index) const
 RefPtr<StorageDevice> AHCIController::device(u32 index) const
 {
  NonnullRefPtrVector<StorageDevice> connected_devices;
- for (size_t index = 0; index < capabilities().ports_count; index++) {
- auto checked_device = device_by_port(index);
+ u32 pi = hba().control_regs.pi;
+ u32 bit = __builtin_ffsl(pi);
+ while (bit) {
+ dbgln_if(AHCI_DEBUG, "Checking implemented port {}, pi {:b}", bit - 1, pi);
+ pi &= ~(1u << (bit - 1));
+ auto checked_device = device_by_port(bit - 1);
+ bit = __builtin_ffsl(pi);
  if (checked_device.is_null())
  continue;
  connected_devices.append(checked_device.release_nonnull());
  }
+ dbgln_if(AHCI_DEBUG, "Connected device count: {}, Index: {}", connected_devices.size(), index);
  if (index >= connected_devices.size())
  return nullptr;
  return connected_devices[index];