bnxt_en: Fix bp->fw_health allocation and free logic.

bp->fw_health needs to be allocated for either the firmware initiated
reset feature or the driver initiated error recovery feature.  The
current code is not allocating bp->fw_health for all the necessary cases.
This patch corrects the logic to allocate bp->fw_health correctly when
needed.  If allocation fails, we clear the feature flags.

We also add the the missing kfree(bp->fw_health) when the driver is
unloaded.  If we get an async reset message from the firmware, we also
need to make sure that we have a valid bp->fw_health before proceeding.

Fixes: 07f83d72 ("bnxt_en: Discover firmware error recovery capabilities.")
Signed-off-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>