dt-bindings: timer: add Andes machine timer

dt-bindings: timer: add Andes machine timer

Add the DT binding documentation for Andes machine timer.

The RISC-V architecture defines a machine timer that provides a real-time
counter and generates timer interrupts. Andes machiner timer (PLMT0) is
the implementation of the machine timer, and it contains memory-mapped
registers (mtime and mtimecmp). This device supports up to 32 cores.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Ben Zong-You Xie <ben717@andestech.com>
Link: https://lore.kernel.org/r/20250711133025.2192404-6-ben717@andestech.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>