wifi: rtw88: check for PCI upstream bridge existence

commit eb101d2 upstream.

pci_upstream_bridge() returns NULL if the device is on a root bus.  If
8821CE is installed in the system with such a PCI topology, the probing
routine will crash.  This has probably been unnoticed as 8821CE is mostly
supplied in laptops where there is a PCI-to-PCI bridge located upstream
from the device.  However the card might be installed on a system with
different configuration.

Check if the bridge does exist for the specific workaround to be applied.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: 24f5e38 ("rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Acked-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20260220094730.49791-1-pchelkin@ispras.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: pchelkin91

drivers/net/wireless/realtek/rtw88/pci.c

@@ -1749,7 +1749,8 @@ int rtw_pci_probe(struct pci_dev *pdev,
 	}
 
 	/* Disable PCIe ASPM L1 while doing NAPI poll for 8821CE */
-	if (rtwdev->chip->id == RTW_CHIP_TYPE_8821C && bridge->vendor == PCI_VENDOR_ID_INTEL)
+	if (rtwdev->chip->id == RTW_CHIP_TYPE_8821C &&
+	    bridge && bridge->vendor == PCI_VENDOR_ID_INTEL)
 		rtwpci->rx_no_aspm = true;
 
 	rtw_pci_phy_cfg(rtwdev);