dt-bindings: riscv: add Zaamo and Zalrsc ISA extension description

Add description for the Zaamo and Zalrsc ISA extension[1].

Link: https://github.com/riscv/riscv-zaamo-zalrsc

 [1]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240619153913.867263-2-cleger@rivosinc.com


Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>