arm64: dts: qcom: sc7280: Move herobrine-r0 to its own dts

The upcoming herobrine-r1 board is really not very similar to
herobrine-r0. Let's get rid of the "herobrine.dtsi" file and stick all
the content in the -r0 dts file directly. We'll also rename the dts so
it's obvious that it's just for -r0.

While renaming, let's actually name the file so it's obvious that
"herobrine" is both the name of the board and the name of the
"baseboard". In other words "herobrine" is an actual board but also
often used as the name of a whole class of similar boards that forked
from a design. While "herobrine-herobrine" is a bit of mouthful it
makes it more obvious which things are part of an actual board rather
than the baseboard.

NOTE: herobrine-rev0's days are likely doomed and this device tree is
likely to be deleted in the future.

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/20220125144316.v2.2.Id9716db8c133bcb14c9413144048f8d00ae2674f@changeid