it8xxx: Improve ifdef expression for IT8XXX drivers
it8xxx: Improve ifdef expression for IT8XXX drivers

IT83XX and IT8XXX2 drivers are not compiled if the flag
CONFIG_USB_PD_TCPM_ITE_ON_CHIP is not defined. So instead
of the first two flags, the ITE_ON_CHIP is used in expression
that undefines CONFIG_USB_PD_TCPC_VCONN

BUG=b:182500469
BRANCH=none
TEST=Use util/compare_build.sh to verify if firmware wasn't changed
     with this commit. Boards tested:
     "icarus kracko haboki cozmo drawcia lantis wheelie volteer delbin"

Signed-off-by: Michał Barnaś <77666125932addc6fc525b281b518fd8fd2203d8@semihalf.com>
Change-Id: If26e855186c56c9cf118e727b8bafe5e3d1ea734
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2919908
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

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