Revert "[MIPS] Make SPARSEMEM selectable on QEMU."

This reverts commit 31473747

.

Another amazing example of patch(1) messing up - lmo changeset
66e8560d11d02bcadc261498471831a6375ad046 was merged twice to kernel.org
and ended up doing this rubbish job.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>