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

sys/x86/x86/cpu_machdep.c

@@ -508,8 +508,6 @@ cpu_reset(void)
 				/* NOTREACHED */
 			}
 		}
-
-		DELAY(1000000);
 	}
 #endif
 	cpu_reset_real();