perf tools: Add arch/*/include/generated/ to .gitignore

perf tools: Add arch/*/include/generated/ to .gitignore

Commit 1b700c997500 ("perf tools: Build syscall table .c header from
kernel's syscall_64.tbl") automatically generates per-arch syscall table
arrays, e.g.:

    arch/x86/include/generated/asm/syscalls_64.c

So add this directory to .gitignore

Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 1b700c997500 ("perf tools: Build syscall table .c header from kernel's syscall_64.tbl")
Link: http://lkml.kernel.org/r/1464343274-19403-1-git-send-email-treeze.taeung@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>