Exynos5: clock: Fix a typo bug in exynos clock init

We intended to clear the bits of CLK_SRC_TOP2 register, instead we were
writing on the reserved bits of src_core1 register. Since the default
value of clk_src_top2 register were itself zero, this typo was not
creating any big issue. But it is better to fix this error for better
readability of the code.

Signed-off-by: Hatim Ali <hatim.rv@samsung.com>
Signed-off-by: Akshay Saraswat <akshay.s@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>