tools: kwboot: Add support for UART boot mode patching for Armada XP/38x

Currently, kwboot only allows dynamic UART boot mode patching for SoCs
with header version 0 (Orion, Kirkwood). This patch now enables this "-p"
feature also for SoCs with header version 1 (Armada XP / 38x etc). With
this its possible now to use the UART boot mode without on images that
are generated for other boot devices, like SPI. So no need to change
BOOT_FROM to "uart" for UART xmodem booting any more.

Signed-off-by: Stefan Roese <sr@denx.de>
Tested-by: Kevin Smith <kevin.smith@elecsyscorp.com>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Cc: Dirk Eibach <eibach@gdsys.de>