arm64: dts: apple: Replace UART clocking TODO with proper documentation

[statick88]

Summary

Replace speculative TODO comments about UART clocking in 7 Apple Silicon .dtsi files with proper documentation explaining why <&clkref> (24 MHz) is correct.

Background

The TODO comments (figure out the clocking properly, there may be a third selectable clock) were misleading. Analysis of the Samsung-compatible UART driver (samsung_tty.c) shows:

• The driver sets num_clks = 1 for the S5L variant, only searching for one baud clock (clk_uart_baud0).
• Baud divisor formula: quot = (rate + (8 * baud)) / (16 * baud)
• With 24 MHz clkref, standard baud rates achieve <0.2% error (115200 baud: 0.16% error).

Both clocks correctly use the 24 MHz reference clock. No third clock is needed or supported by the driver.

Changes

• 7 .dtsi files: t8103.dtsi, t8112.dtsi, t8122.dtsi, t6030.dtsi, t600x-die0.dtsi, t602x-die0.dtsi, t6031-die0.dtsi
• Replaced TODO with explanatory comment documenting the driver analysis

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Signed-off-by: Diego Saavedra dsaavedra88@gmail.com