MIPS: Don't register r4k sched clock when CPUFREQ enabled

MIPS: Don't register r4k sched clock when CPUFREQ enabled

Don't register r4k sched clock when CPUFREQ enabled because sched clock
need a constant frequency.

Signed-off-by: Huacai Chen <[email protected]>
Cc: John Crispin <[email protected]>
Cc: Steven J . Hill <[email protected]>
Cc: Fuxin Zhang <[email protected]>
Cc: Zhangjin Wu <[email protected]>
Cc: [email protected]
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/13820/
Signed-off-by: Ralf Baechle <[email protected]>