Don't use KERN_OPTMZ or KERN_DBG on Linux 2.6

Don't use KERN_OPTMZ or KERN_DBG on Linux 2.6

With 2.6 Linux kernels, we just use the standard Kernel build system.
As this system pays no attention to our settings of KERN_OPTMZ or
KERN_DBG, don't bother setting values for these for 2.6 kernels.

Change-Id: Ibb2302d63ecf3e32a24321028df6a9aad45769fc
Reviewed-on: http://gerrit.openafs.org/4173
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>