MIPS: Update outdated comment

The hard-coded offsets mentioned in this comment seem to not exist
anymore, so remove mention of them from the comment.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6421/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>