Remove "Sticky" recovery mode on Daisy
Remove "Sticky" recovery mode on Daisy

Previously, if you used Esc + Reload + Power to reboot into recovery
mode, you would be stuck in it until you manually rebooted the EC with
"Reload + Power."  This was because the button combo set a switch that
was never un-set.  To fix it, the keyboard_scan function now sets a host
event, that is serviced once, and then cleared.  As a result, the next
time you reboot after triggering recovery mode, it should boot as before
you triggered recovery mode.

BUG=chrome-os-partner:10889
TEST=Boot device in normal mode.  Press Esc + Reload + Power, and boot
from usb.  Power off the device and remove the usb media.  Power on the
device again, and there should be no recovery screens during the boot
process.  Next, repeat these same steps, but from starting in developer
mode.  After recovery, when you reboot, the device should return to
developer mode.

Change-Id: Idcb8dde6f8ba5f680f4d34e61ae0d12992281cbb
Signed-off-by: Charlie Mooney <c4f45ade001857f07012a75265a97cb07f1531f2@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/28710
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

alterapraxisptyltd/chromium-ec,longsleep/ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,md5555/ec,longsleep/ec,mtk09422/chromiumos-platform-ec,fourier49/BIZ_EC,fourier49/BIZ_EC,akappy7/ChromeOS_EC_LED_Diagnostics,eatbyte/chromium-ec,gelraen/cros-ec,mtk09422/chromiumos-platform-ec,gelraen/cros-ec,fourier49/BZ_DEV_EC,gelraen/cros-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,md5555/ec,fourier49/BZ_DEV_EC,gelraen/cros-ec,eatbyte/chromium-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,thehobn/ec,akappy7/ChromeOS_EC_LED_Diagnostics,longsleep/ec,md5555/ec,alterapraxisptyltd/chromium-ec,thehobn/ec,alterapraxisptyltd/chromium-ec,thehobn/ec,longsleep/ec,fourier49/BIZ_EC,coreboot/chrome-ec,mtk09422/chromiumos-platform-ec,fourier49/BIZ_EC,thehobn/ec,md5555/ec,coreboot/chrome-ec,fourier49/BZ_DEV_EC,alterapraxisptyltd/chromium-ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics