perf test record+probe_libc_inet_pton.sh: Use "grep -F" instead of obsolescent "fgrep"

There exists the following warning when executing 'perf test record+probe_libc_inet_pton.sh':

  fgrep: warning: fgrep is obsolescent; using grep -F

This is tested on Fedora 38, the version of grep is 3.8, the latest
version of grep claims the fgrep is obsolete, use "grep -F" instead of
"fgrep" to silence the warning.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: loongson-kernel@lists.loongnix.cn
Link: https://lore.kernel.org/r/1686880567-30017-1-git-send-email-yangtiezhu@loongson.cnSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/record+probe_libc_inet_pton.sh

@@ -14,7 +14,7 @@
 . "$(dirname "$0")/lib/probe_vfs_getname.sh"
 
 libc=$(grep -w libc /proc/self/maps | head -1 | sed -r 's/.*[[:space:]](\/.*)/\1/g')
-nm -Dg $libc 2>/dev/null | fgrep -q inet_pton || exit 254
+nm -Dg $libc 2>/dev/null | grep -F -q inet_pton || exit 254
 
 event_pattern='probe_libc:inet_pton(\_[[:digit:]]+)?'
 
@@ -94,7 +94,7 @@ delete_libc_inet_pton_event() {
 }
 
 # Check for IPv6 interface existence
-ip a sh lo | fgrep -q inet6 || exit 2
+ip a sh lo | grep -F -q inet6 || exit 2
 
 skip_if_no_perf_probe && \
 add_libc_inet_pton_event && \