ARM: EXYNOS: Remove legacy UART initialization code

This patch removes legacy UART initialization code that was used to
set up UART platform devices when booting with ATAGS, which is not
supported on Exynos any more.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>