bnxt_en: Fix logic that disables Bus Master during firmware reset.

The current logic that calls pci_disable_device() in __bnxt_close_nic()
during firmware reset is flawed.  If firmware is still alive, we're
disabling the device too early, causing some firmware commands to
not reach the firmware.

Fix it by moving the logic to bnxt_reset_close().  If firmware is
in fatal condition, we call pci_disable_device() before we free
any of the rings to prevent DMA corruption of the freed rings.  If
firmware is still alive, we call pci_disable_device() after the
last firmware message has been sent.

Fixes: 3bc7d4a3

 ("bnxt_en: Add BNXT_STATE_IN_FW_RESET state.")
Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>