MIPS: Always use r4k_wait_irqoff for MIPSr6
MIPS: Always use r4k_wait_irqoff for MIPSr6

Prior to release 6 of the MIPS architecture it has been implementation
dependent whether masked interrupts cause a wait instruction to return,
so the kernel has effectively had to maintain a whitelist of cores upon
which it is safe to use the r4k_wait_irqoff cpu_wait implementation.
With MIPSr6 this is no longer implementation dependent and
r4k_wait_irqoff can always be used.

Remove the existing I6400 case which will no longer ever be hit, and was
incorrect anyway since I6400 & r6 in general doesn't have the WII bit.

Signed-off-by: Paul Burton <85f1bffadddedccfafc0ae065a06aa636075387f@imgtec.com>
Cc: 562397917b9a8bf316569a848858b12fb417723f@linux-mips.org
Cc: Leonid Yegoshin <d6aca6b5694d055adc6cbbaf8ff810fc31ed7c5d@imgtec.com>
Cc: 2578944098299abf708b08eff6fcf60565553586@vger.kernel.org
Cc: James Hogan <547fa85bb3888a0222eed8ec39e36708605c6d53@imgtec.com>
Cc: Markos Chandras <5cdbcb0e11d2b5ebc39222958c54a1c6329d0c9d@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11210/
Signed-off-by: Ralf Baechle <92f48d309cda194c8eda36aa8f9ae28c488fa208@linux-mips.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs