dt-bindings: interconnect: Add MediaTek EMI Interconnect bindings

dt-bindings: interconnect: Add MediaTek EMI Interconnect bindings

Add bindings for the MediaTek External Memory Interface Interconnect,
which providers support system bandwidth requirements through Dynamic
Voltage Frequency Scaling Resource Collector (DVFSRC) hardware.

This adds bindings for MediaTek MT8183 and MT8195 SoCs.

Note that this is modeled as a subnode of DVFSRC for multiple reasons:
 - Some SoCs have more than one interconnect on the DVFSRC (and two
   different kinds of EMI interconnect, and also a SMI interconnect);

 - Some boards will want to not enable the interconnect driver because
   some of those are not battery powered (so they just keep the knobs
   at full thrust from the bootloader and never care scaling busses);

 - Some DVFSRC interconnect features may depend on firmware.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240610085735.147134-3-angelogioacchino.delregno@collabora.com
Signed-off-by: Georgi Djakov <djakov@kernel.org>