Linux: bdi doesn't always have a name

Linux: bdi doesn't always have a name

The 'name' element of the backing_dev_info structure is new in
2.6.32 - add yet another configure test, and #ifdef to protect our
setting of it.

Change-Id: I0a3e411e571e05771619381bf621d299482c695b
Reviewed-on: http://gerrit.openafs.org/1341
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit a9951410e1cb1a713f9d26a24d6b3cf485f94ac6)
Reviewed-on: http://gerrit.openafs.org/1498
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>