buildroot

tar: remove empty host dependencies definition

Note that host-tar dependencies were broken with automatic derivation
of host dependencies:
host-tar could depend (or not) on host-attr (and even on non-existing
host-acl!), depending on BR2_PACKAGE_BUSYBOX.

Now, host-tar has no dependency.

Signed-off-by: Julien Floret <julien.floret@6wind.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>