selftests: livepatch: set LC_ALL=C to fix locale-dependent test failure

selftests: livepatch: set LC_ALL=C to fix locale-dependent test failure

When executing the command
"make -C tools/testing/selftests TARGETS=livepatch run_tests",
the following error message was reported.

TEST: livepatch interaction with ftrace_enabled sysctl ... not ok
...
livepatch: sysctlo
: setting key "kernel.ftrace_enabled": Device or resource busy
livepatch: sysctl: setting key "kernel.ftrace_enabled": 设备或资源忙
...
ERROR: livepatch kselftest(s) failed
not ok 5 selftests: livepatch: test-ftrace.sh # exit=1

To fix it, set LC_ALL=C.

Signed-off-by: Qiang Ma <maqianga@uniontech.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20260527095929.1504032-1-maqianga@uniontech.com
Signed-off-by: Petr Mladek <pmladek@suse.com>