Bug in GnttabQueryReference

[Connor Davis <connojd@xxxxxxxxxxxxxx>]

Hi All,

There appears to be a bug in xenbus/src/xenbus/gnttab.c:GnttabQueryReference.
The check for a ReadOnly entry uses

    (Context->Table[Reference].frame & GTF_readonly)

instead of

    (Context->Table[Reference].flags & GTF_readonly)

I grepped across all the PV drivers and it looks like this function is
only used for the store and console references, which pass NULL to ReadOnly,
so the bug hasn't actually manifested yet.

Cheers,
Connor Davis