pd: Fix false USB-C DTS detection
pd: Fix false USB-C DTS detection

tcpm_get_cc() returns TYPEC_CC_VOLT_*, not TYPEC_CC_*. Check for RP
rather than non-open to match USB-C spec (Table B-2 Rp/Rp Charging
Current Values for a DTS Source).

BUG=chromium:775542
BRANCH=servo
TEST=Verify donette and guppy are not detected as DTS, verify suzy-qable
is detected as DTS, on kevin DUT.

Signed-off-by: Shawn Nematbakhsh <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Change-Id: I0ff5550e9171ff86b42b489525044bf63827240c
Reviewed-on: https://chromium-review.googlesource.com/733220
Commit-Ready: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Tested-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
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