dt-bindings: interrupt-controller: riscv,cpu-intc: convert to dtschema

dt-bindings: interrupt-controller: riscv,cpu-intc: convert to dtschema

Convert the RISC-V Hart-Level Interrupt Controller (HLIC) to newer
DT schema, Created DT schema based on the .txt file which had
`compatible`, `#interrupt-cells` and `interrupt-controller` as
required properties.
Changes made with respect to original file:
- Changed the example to just use interrupt-controller instead of
using the whole cpu block
- Changed the example compatible string.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Kanak Shilledar <kanakshilledar@gmail.com>
Link: https://lore.kernel.org/r/20240615021507.122035-2-kanakshilledar@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>