ramips: add proper system clock and reset driver support for mt7621

ramips: add proper system clock and reset driver support for mt7621

This series of upstream patches makes the system controller node as a
reset provider[1][2], and it also includes some clock and reset driver
fixes[3][4]. Meanwhile, all clocks and resets properties in the SoC
device tree have been updated to be compatible with the new driver.

[1] https://lore.kernel.org/r/20220110114930.1406665[email protected]
[2] https://lore.kernel.org/r/20220210094859[email protected]
[3] https://lore.kernel.org/r/20221217074806.3225150[email protected]
[4] https://lore.kernel.org/r/20230206083305[email protected]

Tested on RAISECOM MSG1500 X.00

Signed-off-by: John Thomson <[email protected]>
Signed-off-by: Shiji Yang <[email protected]>