selftests/bpf/test_lirc_mode2.sh: Exit with proper code

When test_lirc_mode2_user exec failed, the test report failed but still
exit with 0. Fix it by exiting with an error code.

Another issue is for the LIRCDEV checking. With bash -n, we need to quote
the variable, or it will always be true. So if test_lirc_mode2_user was
not run, just exit with skip code.

Fixes: 6bdd533cee ("bpf: add selftest for lirc_mode2 type program")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220321024149.157861-1-liuhangbin@gmail.com

tools/testing/selftests/bpf/test_lirc_mode2.sh

@@ -3,6 +3,7 @@
 
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
+ret=$ksft_skip
 
 msg="skip all tests:"
 if [ $UID != 0 ]; then
@@ -25,7 +26,7 @@ do
 	fi
 done
 
-if [ -n $LIRCDEV ];
+if [ -n "$LIRCDEV" ];
 then
 	TYPE=lirc_mode2
 	./test_lirc_mode2_user $LIRCDEV $INPUTDEV
@@ -36,3 +37,5 @@ then
 		echo -e ${GREEN}"PASS: $TYPE"${NC}
 	fi
 fi
+
+exit $ret