md: Removing num_sector and replacing start_sector with end_sector

Remove num_sectors from dev_info and replace start_sector with
end_sector.  This makes a lot of comparisons much simpler.

Signed-off-by: Sandeep K Sinha <sandeepksinha@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --cc drivers/md/linear.c
Simple merge

diff --cc drivers/md/linear.h
Simple merge