arm64:dts: Add SP8 PRB VR FS1606

[modolaty]

Add new System VR FS1606 for SP8 PRBs Falcon and Seagull

Tested:

• verified in Falcon and Seagull

[anshaw9]

Looks good overall.

Just one small suggestion:

• We can combine the compatible entries into a single line:
  compatible = "tdk,fs1606a", "pmbus";

• Also, for consistency, we may prefer lowercase hex formatting for addresses:
  reg = <0x09>;
  reg = <0x0a>;

Suggested format:

p1v8aux@09 {
// P1V8_AUX VRM
// TDK: FS1606
compatible = "tdk,fs1606a", "pmbus";
reg = <0x09>;
};

p0v85aux@0a {
// P0V85_AUX VRM
// TDK: FS1606
compatible = "tdk,fs1606a", "pmbus";
reg = <0x0a>;
};