bnx2x: Remove format_fw_ver_t function casts

The return values for format_fw_ver_t callbacks are supposed to be
"int", not "u8". Ultimately, the top-level caller doesn't actually check
the return value at all, but just clean this all up anyway and fix the
prototypes so that casts are no longer needed.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>