sparc64: add missing initialization of folio in tlb_batch_add()

Commit 1a10a44d ("sparc64: implement the new page table range API")
missed initialization of folio variable in tlb_batch_add() which causes
boot tests to crash.

Add missing initialization.

Link: https://lkml.kernel.org/r/20230904174350.GF3223@kernel.org
Fixes: 1a10a44d ("sparc64: implement the new page table range API")
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/sparc/mm/tlb.c

@@ -128,6 +128,7 @@ void tlb_batch_add(struct mm_struct *mm, unsigned long vaddr,
 			goto no_cache_flush;
 
 		/* A real file page? */
+		folio = page_folio(page);
 		mapping = folio_flush_mapping(folio);
 		if (!mapping)
 			goto no_cache_flush;