ARM: EXYNOS: Fix support of Exynos4210 rev0 SoC

This patch extends exynos_init_time() function to handle Exynos4210 rev0
SoC, which differs in availability of system timers and needs different
clocksource initialization.

This makes it possible to use exynos_init_time() function as init_time
callback for all Exynos-based boards, including Universal_C210, which
originally had to use samsung_timer_init().

Signed-off-by: Tomasz Figa <t.figa@samsung.com>