clk: exynos5250: Add enum entries for divider clock of i2s1 and i2s2

This patch adds enum entries for div_i2s1 and div_i2s2 which are
required for i2s1 and i2s2 controllers.

Signed-off-by: Padmavathi Venna <padma.v@samsung.com>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>