MIPS: perf: Cleanup formatting in arch/mips/kernel/perf_event.c

Get rid of a bunch of useless inline declarations, and join a bunch of
improperly split lines.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2793/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>