x86: Remove 1 second DELAY from cpu_reset

On SMP systems, cpu_reset broadcasts a message telling the APs to stop
themselves, and then the BSP waits 1 second before actually resetting
itself; this behaviour dates back to 1998-05-17.

I assume that this delay was added in order to allow the APs to stop
themselves before the BSP resets; but we wait until the APs have all
acknowledged entering the "stopped" state, so it no longer seems to
serve any purpose.

Reviewed by: jhb, kib
Sponsored by: https://www.patreon.com/cperciva
Differential Revision: https://reviews.freebsd.org/D35797