nios2: TLBMISC writes do not require PID bits to be set

TLBMISC_RD does not use PID bits, and when setting invalid TLBs,
the PID is not required because the address will not match.

This is just a tidy up.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>