staging: lustre: lnet-lib: opencode some alloc/free functions.

These functions just call LIBCFS_ALLOC() which in-turn
calls kvmalloc().
In none of these cases is the 'vmalloc' option needed.

LIBCFS_ALLOC also produces a warning if NULL is returned,
but that can be provided with CONFIG_SLAB_DEBUG.

LIBCFS_ALLOC zeros the memory, so we need to use
__GFP_ZERO too.

So with one exception where the alloc function is not trivial,
open-code the alloc and free functions using kmalloc and kfree.

Note that the 'size' used in lnet_md_alloc() is limited and less than
a page because LNET_MAX_IOV is 256, so kvmalloc is not needed.

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