MIPS: Undefine PMD_ORDER for 32-bit builds

MIPS: Undefine PMD_ORDER for 32-bit builds

During an update long ago to conform to 4-level page code, PMD_ORDER was
changed from 0 to 1, despite the fact that a PMD table is not used at
all in a 32-bit MIPS build. PMD_ORDER does not seem to be used in these
builds. Now, it matches PUD_ORDER, a nonsense #define to give a build
failure with informative error.

The older commit that had redefined PMD_ORDER was
commit c6e8b587718c ("Update MIPS to use the 4-level pagetable code
thereby getting rid of the compacrapability headers.")

Signed-off-by: Daniel Silsby <dansilsby@gmail.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: od@zcrc.me
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org