bnxt_en: check and resize NVRAM UPDATE entry before flashing

Resize of the UPDATE entry is required if the image to
be flashed is larger than the available space. Add this step,
otherwise flashing larger firmware images by ethtool or devlink
may fail.

Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Signed-off-by: Vikas Gupta <vikas.gupta@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>