make afsd partition size check be large partition safe

make afsd partition size check be large partition safe

right now the math overflows the 32 bit type for >2tb partitions.
use larger variables to avoid this.

Reviewed-on: http://gerrit.openafs.org/392
Reviewed-by: Matt Benjamin <matt@linuxbox.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit ad1e9c7084e99a67ee7a61c255a6059ebc9190c3)
Change-Id: I75c4cd03dadce5218407a5e663474b2cd22a34ad
Reviewed-on: http://gerrit.openafs.org/961