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>