[Skiboot] [PATCH] gard: print error message when we can't open a flash device

[Stewart Smith]

Jeremy Kerr <jk at ozlabs.org> writes:
> If I run gard on system flash as a non-root user, I get:
>
>   $ ./external/gard/gard list
>   $ echo $?
>   1
>
> which isn't too helpful. This change adds a basic error message to the
> open() failure.

Thanks, applied to master as of 292475cbc4e9