bnxt_en: Fix devlink NVRAM related byte order related issues.

The current code does not do endian swapping between the devlink
parameter and the internal NVRAM representation.  Define a union to
represent the little endian NVRAM data and add 2 helper functions to
copy to and from the NVRAM data with the proper byte swapping.

Fixes: 782a624d ("bnxt_en: Add bnxt_en initial port params table and register it")
Cc: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>