bnxt_en: Improve the status_reliable flag in bp->fw_health.

In order to read the firmware health status, we first need to determine
the register location and then the register may need to be mapped.
There are 2 code paths to do this.  The first one is done early as a
best effort attempt by the function bnxt_try_map_fw_health_reg().  The
second one is done later in the function bnxt_map_fw_health_regs()
after establishing communications with the firmware.  We currently
only set fw_health->status_reliable if we can successfully set up the
health register in the first code path.

Improve the scheme by setting the fw_health->status_reliable flag if
either (or both) code paths can successfully set up the health
register.  This flag is relied upon during run-time when we need to
check the health status.  So this will make it work better.

During ifdown, if the health register is mapped, we need to invalidate
the health register mapping because a potential fw reset will reset
the mapping.  Similarly, we need to do the same after firmware reset
during recovery.  We'll remap it during ifup.

Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Reviewed-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>