ARM: SAMSUNG: Consolidate uncompress subroutine

For mach-exynos, uart_base is a pointer and the value is calculated
in the machine folder. For other machines, uart_base is defined as
a macro in platform directory. For symmetry, the uart_base macro
definition is removed and the uart_base calculation is moved to
specific machine folders.

This would help us consolidating uncompress subroutine for s5p64x0.

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