s390/ptrace: fix PTRACE_GET_LAST_BREAK error handling

[ Upstream commit f9bbf25e7b2b74b52b2f269216a92657774f239c ]

Return -EFAULT if put_user() for the PTRACE_GET_LAST_BREAK
request fails, instead of silently ignoring it.

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>