mac80211: remove redundant check in ieee80211_master_start_xmit (net/mac80211/tx.c)

 - This patch (against the linux-wireless-next git tree) removes a
redundant check in ieee80211_master_start_xmit (net/mac80211/tx.c)
and adjust indentation in this method accordingly.

 In this method, there is no need to call again the
ieee80211_is_data() method; this is checked immediately before, in the
"if" command (we will not enter this block unless ieee80211_is_data()
is true, so that the "and" (&&) condition in that "if" command will be
fullfilled ).

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>