riscv: Remove duplicated GET_RM

The macro GET_RM defined twice in this file, one can be removed.

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
Fixes: 956d705d ("riscv: Unaligned load/store handling for M_MODE")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20241008094141.549248-3-zhangchunyan@iscas.ac.cn


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>