LoongArch: mm: Add p?d_leaf() definitions

commit 303be4b3 upstream.

When I do LTP test, LTP test case ksm06 caused panic at
	break_ksm_pmd_entry
	  -> pmd_leaf (Huge page table but False)
	  -> pte_present (panic)

The reason is pmd_leaf() is not defined, So like commit 501b8104
("mips: mm: add p?d_leaf() definitions") add p?d_leaf() definition for
LoongArch.

Fixes: 09cfefb7

 ("LoongArch: Add memory management")
Cc: stable@vger.kernel.org
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>