kconfig-frontends: Depend on pkgconfig-native

kconfig-frontends: Depend on pkgconfig-native

We were seeing errors like:

| autoreconf: running: /srv/home/pokybuild/yocto-autobuilder/yocto-slave/nightly/build/build/tmp/sysroots/x86_64-linux/usr/bin/autoconf --force
| configure.ac:27: error: possibly undefined macro: AS_IF
|       If this token and others are legitimate, please use m4_pattern_allow.
|       See the Autoconf documentation.
| configure.ac:100: error: possibly undefined macro: AC_MSG_ERROR
| autoreconf: /srv/home/pokybuild/yocto-autobuilder/yocto-slave/nightly/build/build/tmp/sysroots/x86_64-linux/usr/bin/autoconf failed with exit status: 1
| ERROR: autoreconf execution failed.

which turns out to mean the pkgconfig macros were unavailable (thanks for clear
error messages autoconf).

This patch adds in the missing dependency.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>