ARM: S5P64X0: Use common uncompress.h part for plat-samsung

Since uart_base can be set dynamically in arch_detect_cpu(), there is no
need to have a copy of all code locally, just to override UART base
address.

This patch removes any duplicate code in uncompress.h variant of s5p64x0
and implements proper arch_detect_cpu() function to initialize UART with
SoC-specific parameters.

While at it, replace hard-coded register address with macro.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>