package/lvm2: add missing host-pkgconf dependency

configure.ac use PKG_CHECK_MODULES macro to find some libraries dependencies.
So add host-pkgconf in LVM2_DEPENDENCIES.

Fixes:
checking pkg-config is at least version 0.9.0... ./configure: line 9875: [...]/host/bin/pkg-config: No such file or directory

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>