USB-PD: filter duplicated SVID
USB-PD: filter duplicated SVID

We have seen some peripherals may broadcast duplicated SVID, and
this might cause the SM in a weird state in that the SVID disocvering
traverses sequentially by pd_get_next_mode(), and this cause
the SM discovering SVID modes over and over again.

We filter out the duplicated SVID to prevent such scenario.

BUG=b:177285652
TEST=Plug adapter ADLX65YCC3A, and ensure no repeated
     discover_mode for NAKed SVIDs.
BRANCH=none

Change-Id: I68811be039e214c5045fb71bb7025bcc6226a051
Signed-off-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2626795
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>

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