realtek: use DT provided address for timers

realtek: use DT provided address for timers

The I/O base address for the timers was hardcoded into the driver,
or derived from the HW IRQ number as an even more horrible hack. All
supported SoC families have these timers, but with hardcoded addresses
the code cannot be reused right now.

Request the timer's base address from the DT specification, and store it
in a private struct for future reference.

Matching the second interrupt specifier, the address range for the
second timer is added to the DT specification.

Signed-off-by: Sander Vanheule <sander@svanheule.net>