arm64: dts: qcom: sc7280: only enable IPA for boards with a modem

IPA is only needed on a platform if it includes a modem, and not all
SC7280 SoC variants do.  The file "sc7280-herobrine-lte-sku.dtsi" is
used to encapsulate definitions related to Chrome OS SC7280 devices
where a modem is present, and that's the proper place for the IPA
node to be enabled.

Currently IPA is enabled in "sc7280-idp.dtsi", which is included by
DTS files for Qualcomm reference platforms (all of which include the
modem).  That also includes "sc7280-herobrine-lte-sku.dtsi", so
enabling IPA there would make it unnecessary for "sc7280-idp.dtsi"
to enable it.

The only other place IPA is enabled is "sc7280-qcard.dtsi".
That file is included only by "sc7280-herobrine.dtsi", which
is (eventually) included only by these top-level DTS files:
  sc7280-herobrine-crd.dts
  sc7280-herobrine-herobrine-r1.dts
  sc7280-herobrine-evoker.dts
  sc7280-herobrine-evoker-lte.dts
  sc7280-herobrine-villager-r0.dts
  sc7280-herobrine-villager-r1.dts
  sc7280-herobrine-villager-r1-lte.dts
All of but two of these include "sc7280-herobrine-lte-sku.dtsi", and
for those cases, enabling IPA there means there is no need for it to
be enabled in "sc7280-qcard.dtsi".

The two remaining cases will no longer enable IPA as a result of
this change:
  sc7280-herobrine-evoker.dts
  sc7280-herobrine-villager-r1.dts
Both of these have "lte" counterparts, and are meant to represent
board variants that do *not* have a modem.

This is exactly the desired configuration.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Sibi Sankar <quic_sibis@quicinc.com>
Tested-by: Sibi Sankar <quic_sibis@quicinc.com>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221224002126.1518552-1-elder@linaro.org