There's no need to do lots of readlink() calls to canonicalize
a name if we're only going to use stat() on it, since stat()
already chases symlinks.
* src/util/virutil.c (virGetDeviceID): Let stat() do the symlink
chasing.
"virGetDeviceID" could be used across the sources, but it doesn't
relate with this series, and could be done later.
* src/util/virutil.h: (Declare virGetDeviceID, and
vir{Get,Set}DeviceUnprivSGIO)
* src/util/virutil.c: (Implement virGetDeviceID and
vir{Get,Set}DeviceUnprivSGIO)
* src/libvirt_private.syms: Export private symbols of upper helpers