mm: fix some typos and code style problems

fix some typos and code style problems in mm.

gfp.h: s/MAXNODES/MAX_NUMNODES
mmzone.h: s/then/than
rmap.c: s/__vma_split()/__vma_adjust()
swap.c: s/__mod_zone_page_stat/__mod_zone_page_state, s/is is/is
swap_state.c: s/whoes/whose
z3fold.c: code style problem fix in z3fold_unregister_migration
zsmalloc.c: s/of/or, s/give/given

Link: https://lkml.kernel.org/r/20210419083057.64820-1-luoshijie1@huawei.com
Signed-off-by: Shijie Luo <luoshijie1@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>