perf build: Group the NO_SYSCALL_TABLE logic

To help in allowing to disable it from the make command line.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20200529155552.463-2-acme@kernel.org


[ Fixed the logic for the filter part, it should be ifeq, not ifneq ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>