realtek: clock driver: adapt RTL838X DT

realtek: clock driver: adapt RTL838X DT

The clock driver is self contained now. Remove old oscillator definition
from the DT. We need a small SRAM scratchpad area for future use. Add it.
While we are here adapt the SRAM size to the real 128K as the manuals say.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>