Blacklist raspberrypi-kernel from cros_mark_as_stable
Blacklist raspberrypi-kernel from cros_mark_as_stable

BUG=none
TEST=Build raspberrypi-kernel, verify it builds without error

Change-Id: I8ecf7d40ffe60ff86100e4c594c6d945ac89a248
Reviewed-on: https://gerrit.chromium.org/gerrit/43903
Reviewed-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Commit-Queue: Liam McLoughlin <a63c1d66dbd75d3cc434e11bdf376be6f9ff043b@chromium.org>
Tested-by: Liam McLoughlin <a63c1d66dbd75d3cc434e11bdf376be6f9ff043b@chromium.org>

coreos/chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,zhang0137/chromite,zhang0137/chromite,coreos/chromite,chadversary/chromiumos.chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite