perf/core: Move the inline keyword at the beginning of the function declaration

When building perf with W=1 the following warning triggers:

  CC      kernel/events/ring_buffer.o
  kernel/events/ring_buffer.c:105:1: warning: ‘inline’ is not at beginning of declaration [-Wold-style-declaration]
   static bool __always_inline
   ^~~~~~
  ...

Move the inline keyword to the beginning of the function declaration.

Signed-off-by: Mathieu Malaterre <malat@debian.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: trival@kernel.org
Link: http://lkml.kernel.org/r/20180308202856.9378-1-malat@debian.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>