MIPS: Don't probe reserved EntryHi bits.

The patch that adds cpu_probe_vmbits is erroneously writing to reserved
bit 12.  Since we are really only probing high bits, don't write this bit
with a one.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Cc: Guenter Roeck <guenter.roeck@ericsson.com>
Patchwork: http://patchwork.linux-mips.org/patch/949/
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>