selftests: zram: return Kselftest Skip code for skipped tests

When zram test is skipped because of unmet dependencies and/or
unsupported configuration, it exits with error which is treated as
a fail by the Kselftest framework. This leads to false negative result
even when the test could not be run.

Change it to return kselftest skip code when a test gets skipped to
clearly report that the test could not be run.

Kselftest framework SKIP code is 4 and the framework prints appropriate
messages to indicate that the test is skipped.

Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
diff --git a/tools/testing/selftests/zram/zram_lib.sh b/tools/testing/selftests/zram/zram_lib.sh
index f6a9c73..9e73a4f 100755
--- a/tools/testing/selftests/zram/zram_lib.sh
+++ b/tools/testing/selftests/zram/zram_lib.sh
@@ -18,6 +18,9 @@
 dev_makeswap=-1
 dev_mounted=-1
 
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
 trap INT
 
 check_prereqs()
@@ -27,7 +30,7 @@
 
 	if [ $uid -ne 0 ]; then
 		echo $msg must be run as root >&2
-		exit 0
+		exit $ksft_skip
 	fi
 }