ore: Make ore_striping_info and ore_calc_stripe_info public

The struct ore_striping_info will be used later in other
structures. And ore_calc_stripe_info as well. Rename them
make struct ore_striping_info public. ore_calc_stripe_info
is still static, will be made public on first use.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>