common/button: Blink LED for 3 seconds when setting recovery HW_REINIT
common/button: Blink LED for 3 seconds when setting recovery HW_REINIT

If user holds down volume up, volume down and power button for 30
seconds, set HW_REINIT event and blink LED for 3 seconds to indicate
to user that the request was accepted.

BUG=b:37682514
BRANCH=None
TEST=make -j buildall

Change-Id: I6b70d56f50d0a1cfae3fa7f337a34ac487943775
Signed-off-by: Furquan Shaikh <6be5c96c464778f89679b1062a2e0a6af93d2aa5@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/487281
Reviewed-by: Aaron Durbin <af0622ab041e8b0f8e5819838dcc93898196e71f@chromium.org>

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