perf test: Skip perf probe tests when running as non-root

perf trace requires root because it needs to use [ku]probes.
Skip those test when it's not run as root.

Before:
  $ perf test probe
   47: Probe SDT events                                                : Ok
  104: test perf probe of function from different CU                   : FAILED!
  115: perftool-testsuite_probe                                        : FAILED!
  117: Add vfs_getname probe to get syscall args filenames             : FAILED!
  118: probe libc's inet_pton & backtrace it with ping                 : FAILED!
  119: Use vfs_getname probe to get syscall args filenames             : FAILED!

After:
  $ perf test probe
   47: Probe SDT events                                                : Ok
  104: test perf probe of function from different CU                   : Skip
  115: perftool-testsuite_probe                                        : Skip
  117: Add vfs_getname probe to get syscall args filenames             : Skip
  118: probe libc's inet_pton & backtrace it with ping                 : Skip
  119: Use vfs_getname probe to get syscall args filenames             : Skip

Tested-by: Thomas Falcon <thomas.falcon@intel.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20250304022837.1877845-3-namhyung@kernel.org


Signed-off-by: Namhyung Kim <namhyung@kernel.org>