pwm: do *not* set the synchronous reset bit
pwm: do *not* set the synchronous reset bit

This was never cleared.  Need to dig into more, but setting this
doesn't really seem necessary anyway (mbed doesn't do it).

farcaller/zinc,hackndev/zinc,hackndev/zinc,hackndev/zinc,farcaller/zinc,posborne/zinc,mcoffin/zinc,richo/zinc,mcoffin/zinc,mcoffin/zinc,phil-opp/zinc,troplin/zinc,farcaller/zinc,richo/zinc,ntwyman/zinc,phil-opp/zinc,troplin/zinc,phil-opp/zinc,ntwyman/zinc,richo/zinc,mcoffin/zinc,troplin/zinc,posborne/zinc,richo/zinc,ntwyman/zinc,posborne/zinc,ntwyman/zinc,phil-opp/zinc,mcoffin/zinc,troplin/zinc,posborne/zinc,troplin/zinc,hackndev/zinc,farcaller/zinc,hackndev/zinc,richo/zinc,posborne/zinc,phil-opp/zinc,ntwyman/zinc,farcaller/zinc