Revert "MIPS: add PMD table accounting into MIPS'pmd_alloc_one"

This reverts commit 002d8b39 which is
commit ed914d48 upstream.

Commit b2b29d6d (mm: account PMD tables like PTE tables) is
introduced between v5.9 and v5.10, so this fix (commit 002d8b39)
should NOT apply to any pre-5.10 branch.

Signed-off-by: Huang Pei <huangpei@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>