The ACSPCIE_PROXY_CTRL registers within the CTRL_MMR space of TI's J784S4
SoC are used to drive the reference clock to the PCIe Endpoint device via
the PAD IO Buffers. Add the compatible for allowing the PCIe driver to
obtain the regmap for the ACSPCIE_CTRL register within the System
Controller device-tree node in order to enable the PAD IO Buffers.

The Technical Reference Manual for J784S4 SoC with details of the
ASCPCIE_CTRL registers is available at:
https://www.ti.com/lit/zip/spruj52Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240715120936.1150314-2-s-vadapalli@ti.comSigned-off-by: Lee Jones <lee@kernel.org>