OpenBSD: Use FREE instead of KFREE

OpenBSD: Use FREE instead of KFREE

In OpenBSD releases prior to 4.2, use the system (kernel-specific)
FREE macro to release space in the kernel module, not KFREE. The
latter does not exist and results in unresolved symbols when trying
to load the kernel module. (This was undoubtedly a typo.)

Change-Id: Id66704ab4d0928e2ce1234de16bb74fe22f4f9c7
Reviewed-on: http://gerrit.openafs.org/1909
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>