perf top: Allow passing a kallsyms file

This basically replicates what was done for 'perf report' in:

b226a5a72901 ("perf report: Allow user to specify path to kallsyms file")

This should help with resolving eBPF symbols, that are in kallsyms but,
of course, not in vmlinux.

Reported-by: Ivan Babrou <[e-mail]>
Tested-by: Ivan Babrou <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Daniel Borkmann <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: https://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-top.txt

···
 --ignore-vmlinux::
 	Ignore vmlinux files.
 
+--kallsyms=<file>::
+	kallsyms pathname
+
 -m <pages>::
 --mmap-pages=<pages>::
 	Number of mmap data pages (must be a power of two) or size

tools/perf/builtin-top.c

···
 		   "file", "vmlinux pathname"),
 	OPT_BOOLEAN(0, "ignore-vmlinux", &symbol_conf.ignore_vmlinux,
 		    "don't load vmlinux even if found"),
+	OPT_STRING(0, "kallsyms", &symbol_conf.kallsyms_name,
+		   "file", "kallsyms pathname"),
 	OPT_BOOLEAN('K', "hide_kernel_symbols", &top.hide_kernel_symbols,
 		    "hide kernel symbols"),
 	OPT_CALLBACK('m', "mmap-pages", &opts->mmap_pages, "pages",