km/common: fix initial_boot_bank for bootpackages

The initial_boot_bank can be set when more than one application is
used in a bootpackage. But a value n <> 0 never led to booting from
bank n. Instead, bank 0 was booted. This patch fixes this.

Signed-off-by: Thomas Herzmann <thomas.herzmann@keymile.com>
Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
Acked-by: Heiko Schocher <hs@denx.de>
cc: Wolfgang Denk <wd@denx.de>
cc: Detlev Zundel <dzu@denx.de>
cc: Valentin Longchamp <valentin.longchamp@keymile.com>
Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com>