keymile, common: add setting of some environment variables

This patch adds last_stage_init to all keymile boards. And
in the last stage init some environment variables for u-boot
were set. Currently these are pnvramaddr, pram and var address.

Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Kim Phillips <kim.phillips@freescale.com>
cc: Valentin Longchamp <valentin.longchamp@keymile.com>
cc: Wolfgang Denk <wd@denx.de>
cc: Kim Phillips <kim.phillips@freescale.com>