um: Handle tracehook_report_syscall_entry() result

tracehook_report_syscall_entry() is allowed to fail,
in case of failure we have to abort the current syscall.

Signed-off-by: Richard Weinberger <richard@nod.at>

diff --cc arch/um/include/asm/ptrace-generic.h
Simple merge

diff --cc arch/um/kernel/ptrace.c
Simple merge

diff --cc arch/um/kernel/skas/syscall.c
Simple merge