arm64: dts: qcom: sc7280: Delete herobrine-r0

As talked about in commit 61a6262f ("arm64: dts: qcom: sc7280:
Move herobrine-r0 to its own dts"), herobrine evolved pretty
significantly after -r0 and newer revisions are pretty
different. Nobody needs the old boards to keep working, so let's
delete to avoid the maintenance burden.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220308125044.1.I3e4a1a9c102d194698b68661e69efebafec8af1c@changeid