bnx2x: Reuse bnx2x_null_format_ver()

Reuse bnx2x_null_format_ver() in functions where it's appropriated
instead of open coded variant.

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>