Revert "nios2: Convert __pte_free_tlb() to use ptdescs"

This reverts commit 6ebe94ba.

The patch "nios2: Convert __pte_free_tlb() to use ptdescs" was supposed
to go together with a patchset that Vishal Moola had planned taking it
through the mm tree. By just having this patch, all NIOS2 builds are
broken.

Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>