bnxt_en: Fix dmesg log firmware error messages.

Use appropriate firmware request header structure to prepare the
firmware messages.  This avoids the unnecessary conversion of the
fields to 32-bit fields.  Add appropriate endian conversion when
printing out the message fields in dmesg so that they appear correct
in the log.

Reported-by: Rob Swindell <swindell@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>