Unset SRVs which resource are being bound to an RTV

This is the extension of a previously debug-only workaround for
D3D doing the unsetting by itself (with a warning). It made our
state tracking of the bound SRVs out of sync with D3D's and caused
some rendering to not take place.

BUG=427245

Change-Id: Id378030b64fddafbb3d406872a7dfd2c84793221
Reviewed-on: https://chromium-review.googlesource.com/229066
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>