Use the padd op.

Use the padd op.

When the padd operation was added, the change that makes actual use
of it got lost somewhere along the line. Fixed now.

Originally introduction of the padd op:
6220ede6a96d06c53eddd848435764cff96be1b4

Reviewed-on: http://gerrit.openafs.org/471
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>