sniper: Drop references to P970

There are various different boards with the same hardware sold as LG Optimus
Black, such as P970, P970g and KU5900. Since this port is functional for all
variants, it doesn't make sense to keep references to P970.
Signed-off-by: NPaul Kocialkowski <contact@paulk.fr>
Reviewed-by: NTom Rini <trini@konsulko.com>

board/lge/sniper/Makefile

 #
-# LG Optimus Black (P970) codename sniper board
+# LG Optimus Black codename sniper board
 #
 # Copyright (C) 2015 Paul Kocialkowski <contact@paulk.fr>
 #

board/lge/sniper/sniper.c

 /*
- * LG Optimus Black (P970) codename sniper board
+ * LG Optimus Black codename sniper board
  *
  * Copyright (C) 2015 Paul Kocialkowski <contact@paulk.fr>
  *

board/lge/sniper/sniper.h

 /*
- * LG Optimus Black (P970) codename sniper board
+ * LG Optimus Black codename sniper board
  *
  * Copyright (C) 2015 Paul Kocialkowski <contact@paulk.fr>
  *

include/configs/sniper.h

 /*
- * LG Optimus Black (P970) codename sniper config
+ * LG Optimus Black codename sniper config
  *
  * Copyright (C) 2015 Paul Kocialkowski <contact@paulk.fr>
  *