dt-bindings: memory: tegra: Add Tegra234 support

Document the variant of the memory controller and external memory
controllers found on Tegra234 and add some memory client and SMMU
stream ID definitions for use in device tree files.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

include/dt-bindings/clock/tegra234-clock.h

@@ -9,6 +9,15 @@
  * @defgroup bpmp_clock_ids Clock ID's
  * @{
  */
+/**
+ * @brief controls the EMC clock frequency.
+ * @details Doing a clk_set_rate on this clock will select the
+ * appropriate clock source, program the source rate and execute a
+ * specific sequence to switch to the new clock source for both memory
+ * controllers. This can be used to control the balance between memory
+ * throughput and memory controller power.
+ */
+#define TEGRA234_CLK_EMC			31U
 /** @brief output of gate CLK_ENB_FUSE */
 #define TEGRA234_CLK_FUSE			40U
 /** @brief output of mux controlled by CLK_RST_CONTROLLER_CLK_SOURCE_SDMMC4 */