perf tests vmlinux-kallsyms: Use machine__find_kernel_function(_by_name)

perf tests vmlinux-kallsyms: Use machine__find_kernel_function(_by_name)

We had this for ages, IIRC for 'perf probe' use initially, so use them
instead of the variants that pass the map_type, that is going away.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-x1jpogsvj822sh0q8leiaoep@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>