signal/x86: Remove task parameter from send_sigtrap

The send_sigtrap function is always called with task == current.  Make
that explicit by removing the task parameter.

This also makes it clear that the x86 send_sigtrap passes current
into force_sig_fault.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>