This does the same as 23b44e8d,
but for arm:

Don't call KiUserExceptionDispatcher directly on the stack pointer
stored in the CONTEXT, but use the one stored in syscall_frame
(which includes the stack allocation in e.g. RtlRaiseException).
Signed-off-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>