kselftest/arm64: signal: Skip SVE signal test if not enough VLs supported

On platform where SVE is supported but there are less than 2 VLs available
the signal SVE change test should be skipped instead of failing.
Reported-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Andre Przywara <andre.przywara@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220524103149.2802-1-cristian.marussi@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

tools/testing/selftests/arm64/signal/testcases/fake_sigreturn_sve_change_vl.c

@@ -6,6 +6,7 @@
  * supported and is expected to segfault.
  */
 
+#include <kselftest.h>
 #include <signal.h>
 #include <ucontext.h>
 #include <sys/prctl.h>
@@ -40,6 +41,7 @@ static bool sve_get_vls(struct tdescr *td)
 	/* We need at least two VLs */
 	if (nvls < 2) {
 		fprintf(stderr, "Only %d VL supported\n", nvls);
+		td->result = KSFT_SKIP;
 		return false;
 	}