dt-bindings: soc: xlnx: extract xlnx, vcu-settings to separate binding

dt-bindings: soc: xlnx: extract xlnx, vcu-settings to separate binding

The xlnx,vcu binding comprises two adjacent register banks:

The first register bank ("vcu_slcr") contains registers for setting the
clocks of the vcu and controlling the performance monitors. The second
bank ("logicoreip") contains the configuration settings of the video codec
unit, which are set before synthesizing the bitstream.

Drivers that drive the actual video codec unit need to read the
registers from the logicoreip register bank for configuring the vcu
firmware.

As logicoreip is a too generic name for this register bank, use
"vcu-settings" as a binding name, because the register bank basically
provides the configuration settings of the VCU.

Therefore, add the vcu-settings binding to provide a syscon interface
for other drivers to read these registers.

The alternative would have been to merge the two register banks of the
xlnx,vcu binding into one register bank and make xlnx,vcu provide a
syscon interface, but that would lead to more incompatibility than
making second register bank of xlnx,vcu optional.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201109134818.4159342-3-m.tretter@pengutronix.de
Signed-off-by: Michal Simek <michal.simek@xilinx.com>