i3c: dw: Add some functions for reusability

Separate logic for setting intr/thld registers in a func.
Also modify enable function to take care of setting all fields in DEVICE_CTRL.
These functions can be reused later for power management.

Signed-off-by: Aniket <aniketmaurya@google.com>
Link: https://lore.kernel.org/r/20240708062103.3296587-3-aniketmaurya@google.com


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>