MIPS: Allow RIXI for 32-bit kernels on MIPS64

MIPS: Allow RIXI for 32-bit kernels on MIPS64

Commit 63a7b9098867 ("MIPS: Don't use RI/XI with 32-bit kernels on
64-bit CPUs") prevented use of RIXI on MIPS64 systems, stating that the
"TLB handlers cannot handle this case". What they actually couldn't
handle was cases where there were less fill bits in the Entry{Lo,Hi}
registers than bits used by software in PTEs. The handlers can now deal
with this case, so enable RIXI for MIPS32 kernels on MIPS64 systems.

Note that beyond the obvious benefits provided by having RIXI on such
systems, this is required for systems implementing MIPSr6 where RIXI
cannot be disabled.

This reverts commit 63a7b9098867 ("MIPS: Don't use RI/XI with 32-bit
kernels on 64-bit CPUs").

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Joshua Kinard <kumba@gentoo.org>
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11219/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>