powerpc/83xx/km: use tuxx1.h for kmsupx5 target

This additional header is unneeded, we can use the tuxx1.h for this
target.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
cc: Kim Phillips <kim.phillips@freescale.com>
cc: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Gerlando Falauto <gerlando.falauto@keymile.com>
cc: Heiko Schocher <hs@denx.de>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>