selftests/x86/syscall: Fix coccinelle WARNING recommending the use of ARRAY_SIZE()

Coccinelle gives WARNING recommending the use of ARRAY_SIZE() macro definition
to improve the code readability:

  ./tools/testing/selftests/x86/syscall_numbering.c:316:35-36: WARNING: Use ARRAY_SIZE

Fixes: 15c82d98 ("selftests/x86/syscall: Update and extend syscall_numbering_64")
Signed-off-by: Mirsad Todorovac <mtodorovac69@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Link: https://lore.kernel.org/r/20241101111523.1293193-2-mtodorovac69@gmail.com