perf bench futex: Call the futex syscall from a function

In preparation for a more complex futex() function let's convert the
current macro into two functions. We need two functions to avoid
compiler failures as the macro is overloaded.

This will allow us to include pre-processor conditionals in the futex
syscall functions.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alistair Francis <alistair23@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-riscv@lists.infradead.org
Link: http://lore.kernel.org/lkml/20211022013343.2262938-1-alistair.francis@opensource.wdc.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>