driver/touchpad_st.c: implement touchpad fw update
driver/touchpad_st.c: implement touchpad fw update

BRANCH=none
BUG=b:70482333
TEST=make BOARD=whiskers
TEST=sudo ./extra/usb_updater/usb_updater2 -d 18d1:5030 -p <file>
Signed-off-by: Wei-Han Chen <5413a119f383c3f4549c3ef659403f393bf06e9d@chromium.org>

Change-Id: I6e3e73a01571ae4cf31891edca588c44e5f41194
Reviewed-on: https://chromium-review.googlesource.com/958896
Commit-Ready: Wei-Han Chen <5413a119f383c3f4549c3ef659403f393bf06e9d@chromium.org>
Tested-by: Wei-Han Chen <5413a119f383c3f4549c3ef659403f393bf06e9d@chromium.org>
Reviewed-by: Nicolas Boichat <f3daba1cdc403799935674d3cd4b0e5bd1804232@chromium.org>

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