ARM: EXYNOS: Consolidate CPU init code

cpu_table was used to distinguish between different Exynos4 and 5
SoCs and based on the type do the initialization and io mapping.
exynos_init is dummy and no longer needed as we do a DT based booting.
By having a common io mapping function we can get rid of the whole
table and avoid populating it for every SoC.

Tested on Exynos4210, 5250 and 5420 based boards.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Tested-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>