arm/km: remove portl2.h and use km_kirkwood instead

The additional headerfile is unneeded here, we can use the generic
km_kirkwood.h instead. And we can use the better config option
KM_PIGGY4_88E6061 for the specific features for boards with this
design in km_arm.c.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Gerlando Falauto <gerlando.falauto@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>
diff --git a/boards.cfg b/boards.cfg
index 003c2af..db7902f 100644
--- a/boards.cfg
+++ b/boards.cfg
@@ -145,7 +145,7 @@
 kmnusa                       arm         arm926ejs   km_arm              keymile        kirkwood    km_kirkwood:KM_NUSA
 mgcoge3un                    arm         arm926ejs   km_arm              keymile        kirkwood    km_kirkwood:KM_MGCOGE3UN
 kmcoge5un                    arm         arm926ejs   km_arm              keymile        kirkwood    km_kirkwood:KM_COGE5UN
-portl2                       arm         arm926ejs   km_arm              keymile        kirkwood
+portl2                       arm         arm926ejs   km_arm              keymile        kirkwood    km_kirkwood:KM_PORTL2
 inetspace_v2                 arm         arm926ejs   netspace_v2         LaCie          kirkwood	lacie_kw:INETSPACE_V2
 net2big_v2                   arm         arm926ejs   net2big_v2          LaCie          kirkwood	lacie_kw:NET2BIG_V2
 netspace_max_v2              arm         arm926ejs   netspace_v2         LaCie          kirkwood	lacie_kw:NETSPACE_MAX_V2