perf trace: Allocate syscall stats only if summary is on

perf trace: Allocate syscall stats only if summary is on

The syscall stats are used only when summary is requested.  Let's avoid
unnecessary operations.  While at it, let's pass 'trace' pointer
directly instead of passing 'output' file pointer and 'summary' option
in the 'trace' separately.

Reviewed-by: Howard Chu <howardchu95@gmail.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20250205205443.1986408-2-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>