selftests: riscv: Add license to cfi selftest

The cfi selftest was missing a license so add it.

Signed-off-by: Charlie Jenkins <thecharlesjenkins@gmail.com>
Reviewed-by: Deepak Gupta <debug@rivosinc.com>
Link: https://patch.msgid.link/20260309-fix_selftests-v2-4-9d5a553a531e@gmail.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>

tools/testing/selftests/riscv/cfi/Makefile

diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile
index 96a4dc4..93b4738 100644
--- a/tools/testing/selftests/riscv/cfi/Makefile
+++ b/tools/testing/selftests/riscv/cfi/Makefile
@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
 CFLAGS += $(KHDR_INCLUDES)
 CFLAGS += -I$(top_srcdir)/tools/include