package_ipk.bbclass: use common function to write relationship fields

package_ipk.bbclass: use common function to write relationship fields

* A function write_dep_field() was added to do_package_ipk() to
  ensure explode_deps is called for every field and to simplify
  the code.

* The following statement was removed from do_package_ipk():

  if not '-locale-' and not '-dbg' and not '-dev' in pkgname:
      rdepends.append('%s-locale*' % pkgname)

  It was added in November 2008, but can never evaluate to true.

  See commit a045dfacf6f2541e0f410d9d109581f181303756

Signed-off-by: Andreas Oberritter <obi@opendreambox.org>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Tom Rini <tom_rini@mentor.com>