mm/hugetlb: have CONFIG_HUGETLB_PAGE select CONFIG_XARRAY_MULTI

After commit a08c7193 "mm/filemap: remove hugetlb special casing in
filemap.c", hugetlb pages are stored in the page cache in base page sized
indexes.  This leads to multi index stores in the xarray which is only
supporting through CONFIG_XARRAY_MULTI.  The other page cache user of
multi index stores ,THP, selects XARRAY_MULTI.  Have CONFIG_HUGETLB_PAGE
follow this behavior as well to avoid the BUG() with a CONFIG_HUGETLB_PAGE
&& !CONFIG_XARRAY_MULTI config.

Link: https://lkml.kernel.org/r/20231204183234.348697-1-sidhartha.kumar@oracle.com
Fixes: a08c7193 ("mm/filemap: remove hugetlb special casing in filemap.c")
Signed-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/Kconfig

@@ -268,6 +268,7 @@ config HUGETLBFS
 
 config HUGETLB_PAGE
 	def_bool HUGETLBFS
+	select XARRAY_MULTI
 
 config HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 	def_bool HUGETLB_PAGE