ftrace: Disable caching by default
ftrace: Disable caching by default

There are some issues with caching at the moment which I haven't been
able to debug but that are confirmed as affecting multiple
people. Until we can find the time to fix the issue, let's disable
caching by default.

bjackman/trappy,ARM-software/trappy,ARM-software/trappy,bjackman/trappy,bjackman/trappy,bjackman/trappy,ARM-software/trappy,ARM-software/trappy