bnxt_en: Retrieve coredump and crashdump size via FW command

Recent firmware provides coredump and crashdump size info via
DBG_QCFG command. Read the dump sizes from firmware, instead of
computing in the driver. This patch reduces the time taken
to collect the dump via ethtool.

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>