[PATCH] powerc: Update asm-prototypes.h comment

[Russell Currey]

On Fri, 2022-06-17 at 18:02 +1000, Michael Ellerman wrote:
> This header was recently cleaned up in commit 76222808fc25 ("powerpc:
> Move C prototypes out of asm-prototypes.h"), update the comment to
> reflect it's proper purpose.
> 
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Hi Michael, subject says "powerc" instead of "powerpc".

- clippy