proc: switch /proc/meminfo to seq_file

and move it to fs/proc/meminfo.c while I'm at it.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 32e0ef0..e1c8afc 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -27,7 +27,7 @@
 void __unmap_hugepage_range(struct vm_area_struct *,
 			unsigned long, unsigned long, struct page *);
 int hugetlb_prefault(struct address_space *, struct vm_area_struct *);
-int hugetlb_report_meminfo(char *);
+void hugetlb_report_meminfo(struct seq_file *);
 int hugetlb_report_node_meminfo(int, char *);
 unsigned long hugetlb_total_pages(void);
 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
@@ -79,7 +79,9 @@
 #define copy_hugetlb_page_range(src, dst, vma)	({ BUG(); 0; })
 #define hugetlb_prefault(mapping, vma)		({ BUG(); 0; })
 #define unmap_hugepage_range(vma, start, end, page)	BUG()
-#define hugetlb_report_meminfo(buf)		0
+static inline void hugetlb_report_meminfo(struct seq_file *m)
+{
+}
 #define hugetlb_report_node_meminfo(n, buf)	0
 #define follow_huge_pmd(mm, addr, pmd, write)	NULL
 #define follow_huge_pud(mm, addr, pud, write)	NULL