list-packageconfig-flags: print PN instead of P
P (which is ${PN}-${PV}) isn't terribly useful in this context - we
don't really care what the version is, but we do want to know what the
recipe is so we can find it or set PACKAGECONFIG_pn-<PN> in our
configuration, so display ${PN} instead.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>