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/20220110114930.1406665-2-sergio.paracuellos@gmail.com
[2] https://lore.kernel.org/r/20220210094859.927868-2-sergio.paracuellos@gmail.com
[3] https://lore.kernel.org/r/20221217074806.3225150-1-sergio.paracuellos@gmail.com
[4] https://lore.kernel.org/r/20230206083305.147582-1-sergio.paracuellos@gmail.com

Tested on RAISECOM MSG1500 X.00

Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>
Signed-off-by: Shiji Yang <yangshiji66@qq.com>