ec_chip_mchp: Clear ADC sticky hardware status before starting.
ec_chip_mchp: Clear ADC sticky hardware status before starting.

Before starting an ADC conversion clear sticky hardware status
in ADC and interrupt aggregator.

BRANCH=none
BUG=
TEST=Build boards using chip mchp and check for spurious
ADC interrupts.
CQ-DEPEND=CL:1053576

Change-Id: I48b07ecaac2976c5e06e23a4ecf4397ed41c89d1
Signed-off-by: scott worley <186210b307f58d6c0a191337b635ed93ad075837@microchip.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/1053867
Commit-Ready: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Tested-by: Scott Worley <186210b307f58d6c0a191337b635ed93ad075837@microchip.corp-partner.google.com>
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

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