scripts/gdb: implement x86_page_ops in mm.py

scripts/gdb: implement x86_page_ops in mm.py

Implement all member functions of x86_page_ops strictly following the
logic of aarch64_page_ops.

This includes full support for SPARSEMEM and standard page translation
functions.

This fixes compatibility with 'lx-' commands on x86_64, preventing
AttributeErrors when using lx-pfn_to_page and others.

Link: https://lkml.kernel.org/r/20260202034241.649268-1-hsj0512@snu.ac.kr
Signed-off-by: Seongjun Hong <hsj0512@snu.ac.kr>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>