dt-bindings: net: qcom,ipa: Add sram property for describing IMEM slice

The IPA driver currently grabs a slice of IMEM through hardcoded
addresses. Not only is that ugly and against the principles of DT,
but it also creates a situation where two distinct platforms
implementing the same version of IPA would need to be hardcoded
together and matched at runtime.

Instead, do the sane thing and accept a handle to said region directly.

Don't make it required on purpose, as it's not there on ancient
implementations (currently unsupported) and we're not yet done with
filling the data across al DTs.

Reviewed-by: Alex Elder <elder@riscstar.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://patch.msgid.link/20260302-topic-ipa_imem-v6-2-c0ebbf3eae9f@oss.qualcomm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/qcom,ipa.yaml

@@ -165,6 +165,13 @@ properties:
       initializing IPA hardware.  Optional, and only used when
       Trust Zone performs early initialization.
 
+  sram:
+    maxItems: 1
+    description:
+      A reference to an additional region residing in IMEM (special
+      on-chip SRAM), which is accessed by the IPA firmware and needs
+      to be IOMMU-mapped from the OS.
+
 required:
   - compatible
   - iommus