perf tools: Clean 'generated' directory used for creating the syscall table on x86

Remove generated directory tools/perf/arch/x86/include/generated.

Signed-off-by: Andreas Wendleder <andreas.wendleder@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
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>
Link: http://lore.kernel.org/lkml/20210301185642.163396-1-gonsolo@gmail.com


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