cr50: add closed loop reset property to mistral
cr50: add closed loop reset property to mistral

BUG=b:123544145
BRANCH=cr50
TEST=make buildall -j

Change-Id: I39309c73957f0698b573342880a083d14077519f
Signed-off-by: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1480712
Commit-Ready: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@chromium.org>
Tested-by: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@chromium.org>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec