carl9170: Add support for NL80211_IFTYPE_MESH_POINT interfaces

This patch contains following modifications:

- Add mesh capabilities on fw.c to permit creation of mesh
  interfaces using this driver.

- Modify carl9170_set_operating_mode, to use AP-style beaconing
  with mesh interfaces.

- Allow beacon updates for NL80211_IFTYPE_MESH_POINT type in
  carl9170_handle_command_response.

- Add NL80211_IFTYPE_MESH_POINT case on carl9170_op_add_interfaces to
  support mesh/ap/sta virtual interface combinations.

Signed-off-by: Javier Lopez <jlopex@cozybit.com>
Acked-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>