Let the distro control whether we include hostap or madwifi.

Let the distro control whether we include hostap or madwifi.

- Add base_ifelse convenience function to base.bbclass.
- Replace all conditionals in the recipes relating to hostap and madwifi to
  look for their name in COMBINED_FEATURES rather than looking for specific buses (pci, pcmcia).
- Change the default COMBINED_FEATURES to enable:
  - madwifi, when:
    - distro has pci, wifi, and madwifi in its features
    - machine has pci in its features
  - hostap, when:
    - 'wifi' and 'hostap' are in distro features
    - either 'pci' or 'pcmcia' are in both distro and machine features

Signed-off-by: Chris Larson <clarson@mvista.com>