Correct initialization in LaneCtrl

[donggyukim]

This seems to be necessary.

[colinschmidt]

How long did you hold reset? Pipelined reset in Hwacha is a bit longer than in Rocket.

[donggyukim]

5 cycles. But, I believe this is due to:
https://github.com/ucb-bar/hwacha/blob/master/src/main/scala/lane-ctrl.scala#L66

If its value is greater than nSlices, it'll unexpectedly fire.

I actually got this assertion at the beginning of simulation:

Assertion failed: check sreg sched logic vqu_0
    at lane.scala:184 assert(!uop.valid || !uop.bits.sreg(i) || ctrl.io.uop.sreg(ri).valid, "check sreg sched logic "+name+"_"+i)