RISC-V: Fix a comment typo in riscv_of_parent_hartid()

This fixes a typo in a comment that is both obvious and went unnoticed.
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Fixes: a9b20260 ("RISC-V: Improve /proc/cpuinfo output for ISA extensions")
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/cpu.c

@@ -73,7 +73,7 @@ int riscv_of_parent_hartid(struct device_node *node)
  * Here are the ordering rules of extension naming defined by RISC-V
  * specification :
  * 1. All extensions should be separated from other multi-letter extensions
- *    from other multi-letter extensions by an underscore.
+ *    by an underscore.
  * 2. The first letter following the 'Z' conventionally indicates the most
  *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
  *    If multiple 'Z' extensions are named, they should be ordered first