[U-Boot] exynos: please check compiler warning

Dear Padmavathi Venna,

Please check below compiler warning. It can be made a serious problem.

arch/arm/cpu/armv7/exynos/clock.c: In function 'clock_get_periph_rate': arch/arm/cpu/armv7/exynos/clock.c:264:47: warning: array subscript is above array bounds [-Warray-bounds] struct clk_bit_info *bit_info = &clk_bit_info[peripheral]; ^ arch/arm/cpu/armv7/exynos/clock.c:264:47: warning: array subscript is above array bounds [-Warray-bounds]