perf test vmlinux-kallsyms: Ignore aliases to _etext when searching on kallsyms

perf test vmlinux-kallsyms: Ignore aliases to _etext when searching on kallsyms

No need to search for aliases for the symbol that marks the end of the
kernel text segment, the following patch will make such symbols not to
be found when searching in the kallsyms maps causing this test to fail.

So as a prep patch to avoid breaking bisection, ignore such symbols.

Tested-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Link: https://lkml.kernel.org/n/tip-qfwuih8cvmk9doh7k5k244eq@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>