configure: --with-linux-kernel-packaging should default to disabled

configure: --with-linux-kernel-packaging should default to disabled

the test for this build feature is reversed.  by default, the value for
with_linux_kernel_packaging will not be defined which makes the existing
test pick MPS='SP' instead of LINUX_WHICH_MODULES.  based on the configure
help messages, this would appear to be an opt-in not an opt-out.

...
Optional Packages:
...
  --with-linux-kernel-packaging
                          use standard naming conventions to aid Linux kernel
                          build packaging (disables MPS, sets the kernel
                          module name to openafs.ko, and installs kernel
                          modules into the standard Linux location)
...

Reviewed-on: http://gerrit.openafs.org/2869
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 87e96c30e069a2379365c9947a311e700cf51c4d)
Change-Id: Id46afcb341104795c8e206261a2b1dfac289f37b
Reviewed-on: http://gerrit.openafs.org/2938
Tested-by: Derrick Brashear <shadow@dementia.org>