selftests/mm: skip test if application doesn't has root privileges

The test depends on writing to nr_hugepages which isn't possible without
root privileges.  So skip the test in this case.

Link: https://lkml.kernel.org/r/20240101083614.1076768-2-usama.anjum@collabora.com
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Muhammad Usama Anjum

tools/testing/selftests/mm/compaction_test.c

@@ -173,7 +173,7 @@ int main(int argc, char **argv)
 
 	ksft_print_header();
 
-	if (prereq() != 0)
+	if (prereq() || geteuid())
 		return ksft_exit_pass();
 
 	ksft_set_plan(1);