dt-bindings: timer: Add SiFive CLINT2

Add compatible string and property for the SiFive CLINT v2. The SiFive
CLINT v2 is incompatible with the SiFive CLINT v0 due to differences
in their control methods.

Signed-off-by: Nick Hu <nick.hu@sifive.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250321083507.25298-1-nick.hu@sifive.com


Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>