resize_reiserfs: fix > 8TB printf formatting

When performing an offline resize of a file system that will grow
beyond 8 TB, we see negative block counts:

ReiserFS report:
blocksize             4096
block count           -1610612480 (1879048192)
free blocks           -1610702612 (1878982637)
bitmap block count    0 (57344)

The values are passed around appropriately but are printed
incorrectly.

Reported-by: Jimb Esser <wasteland@gmail.com>
Signed-off-by: Jeff Mahoney <jeffm@suse.com>