brcm80211: fix sparse endianess error in mac80211_if.c

The ht capabilities provided upon registration with mac80211 must
be in little endian. This was fixed adding cpu_to_le16() conversion.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>