bnxt_en: Disable/enable Bus master during suspend/resume.

Disable Bus master during suspend to prevent DMAs after the device
goes into D3hot state.  The new 57500 devices may continue to DMA
from context memory after the system goes into D3hot state.  This
may cause some PCIe errors on some system.  Re-enable it during resume.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>