mm: rmap: use the correct parameter name for DEFINE_PAGE_VMA_WALK

mm: rmap: use the correct parameter name for DEFINE_PAGE_VMA_WALK

The parameter used by DEFINE_PAGE_VMA_WALK is _page not page, fix the
parameter name.  It didn't cause any build error, it is probably because
the only caller is write_protect_page() from ksm.c, which pass in page.

Link: https://lkml.kernel.org/r/20220512174551.81279-1-shy828301@gmail.com
Fixes: 8d8351895f80 ("mm: Convert page_vma_mapped_walk to work on PFNs")
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>