linux-imx

[S390] clear TIF_SINGLE_STEP for new process.

Clear the TIF_SINGLE_STEP bit in copy_thread. The new process did not get
a PER event of its own. It is wrong deliver a SIGTRAP that was meant for
the parent process.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>