x86/traps: Shift fill_trap_info() from DO_ERROR_INFO() to do_error_trap()

Move the callsite of fill_trap_info() into do_error_trap() and remove
the "siginfo_t *info" argument.

This obviously breaks DO_ERROR() which passed info == NULL, we simply
change fill_trap_info() to return "siginfo_t *" and add the "default"
case which returns SEND_SIG_PRIV.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>