[S390] ftrace: add function trace mcount test support

Add support for early test if the function tracer is enabled or
disabled. Saves some extra function calls.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2 files changed