tests: soak helper ignores the CPU SRSO advisory

tests/vm/soak-helper.sh

@@ -7,7 +7,10 @@ slab)
 	grep -E '^(pf|pfk)' /proc/slabinfo | tr -s ' ' | cut -d' ' -f1,3 | sort
 	;;
 dmesg)
-	dmesg | grep -E 'BUG:|WARNING:|Oops|general protection|kernel BUG' || true
+	# the CPU's Speculative Return Stack Overflow advisory is a kernel
+	# build/CPU feature notice, not a fault of this module
+	dmesg | grep -E 'BUG:|WARNING:|Oops|general protection|kernel BUG' \
+		| grep -v 'Speculative Return Stack Overflow' || true
 	;;
 states)
 	/opt/pf/pfctl -s states 2>/dev/null | grep -c 'icmp' || true