bnxt_en: Shutdown FW DMA in bnxt_shutdown()

In the Linux kernel, the following vulnerability has been resolved: 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.