chip/host/system: Fix parameter to scanf
chip/host/system: Fix parameter to scanf

value is an integer, so we should use %u, not %lu.

BRANCH=none
BUG=chromium:854924
TEST=make CC=clang run-flash -j (issue only shows up with clang)

Change-Id: Ifc13792dfed548f897c451790c73ad47aa8496ba
Signed-off-by: Nicolas Boichat <f3daba1cdc403799935674d3cd4b0e5bd1804232@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1109660
Reviewed-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

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