bnxt_en: Shutdown FW DMA in bnxt_shutdown()

The netif_close() call in bnxt_shutdown() only stops packet DMA.  There
may be FW DMA for trace logging (recently added) that will continue.  If
we kexec to a new kernel, the DMA will corrupt memory in the new kernel.

Add bnxt_hwrm_func_drv_unrgtr() to unregister the driver from the FW.
This will stop the FW DMA.  In case the call fails, call pcie_flr() to
reset the function and stop the DMA.

Fixes: 24d694a ("bnxt_en: Allocate backing store memory for FW trace logs")
Reported-by: Jakub Kicinski <kicinski@meta.com>
Reviewed-by: Damodharam Ammepalli <damodharam.ammepalli@broadcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20251104005700.542174-2-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Michael Chan

drivers/net/ethernet/broadcom/bnxt/bnxt.c

@@ -16892,6 +16892,10 @@ static void bnxt_shutdown(struct pci_dev *pdev)
 	if (netif_running(dev))
 		netif_close(dev);
 
+	if (bnxt_hwrm_func_drv_unrgtr(bp)) {
+		pcie_flr(pdev);
+		goto shutdown_exit;
+	}
 	bnxt_ptp_clear(bp);
 	bnxt_clear_int_mode(bp);
 	pci_disable_device(pdev);