ux500: fix uncompressor UART address for U5500

The uncompress code for zImage uses the UART to print status messages,
this was hard coded to use UART2 for the U8500 platform. This patch
checks at run time which platform it is run on. U5500 uses UART0 as
console UART.

Signed-off-by: Carl-Johan Irekvist <carl-johan.irekvist@stericsson.com>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>