mm: move kvmalloc-related functions to slab.h

mm: move kvmalloc-related functions to slab.h

Not all files in the kernel should include mm.h.  Migrating callers from
kmalloc to kvmalloc is easier if the kvmalloc functions are in slab.h.

[akpm@linux-foundation.org: move the new kvrealloc() also]
Link: https://lkml.kernel.org/r/20210622215757.3525604-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>