libertas: correct sparse warnings

  CHECK   drivers/net/wireless/libertas/cfg.c
drivers/net/wireless/libertas/cfg.c:493:19: warning: cast to restricted __le16
  CHECK   drivers/net/wireless/libertas/mesh.c
drivers/net/wireless/libertas/mesh.c:577:16: warning: incorrect type in assignment (different base types)
drivers/net/wireless/libertas/mesh.c:577:16:    expected restricted __le32 [addressable] [assigned] [usertype] id
drivers/net/wireless/libertas/mesh.c:577:16:    got bool

Signed-off-by: John W. Linville <linville@tuxdriver.com>