buildroot

util-linux: fix partx build breakage

addpart, delpart and partx are enabled by default so --disable now to
avoid build breaking when we lack libblkid.
Also select libblkid when it's enabled now.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>