staging: lustre: improve some libcfs_kvzalloc calls.

Using vmalloc with GFP_NOFS is not supported as vmalloc
performs some internal allocations with GFP_KERNEL.

So in cases where the size passed to libcfs_kvzalloc()
is clearly at most 1 page, convert to kzalloc().
In cases where the call clearly doesn't hold any
filesystem locks, convert to GFP_KERNEL.

Unfortunately there are many more that are not easy to fix.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>