MIPS: call set_cpu_online() on cpu being brought up with irq disabled

MIPS: call set_cpu_online() on cpu being brought up with irq disabled

To prevent a problem as commit 5fbd036b [sched: Cleanup cpu_active madness]
and commit 2baab4e9 [sched: Fix select_fallback_rq() vs cpu_active/cpu_online]
try to resolve, move set_cpu_online() to the brought up CPU and with irq
disabled.

Signed-off-by: Yong Zhang <[email protected]>
Cc: Sergei Shtylyov <[email protected]>
Cc: David Daney <[email protected]>
Acked-by: David Daney <[email protected]>
Patchwork: https://patchwork.linux-mips.org/patch/3851/
Signed-off-by: Ralf Baechle <[email protected]>