ARM: davinci: da850: fix infinite loop in clk_set_rate()

The aemif clock is added twice to the lookup table in da850.c. This
breaks the children list of pll0_sysclk3 as we're using the same list
links in struct clk. When calling clk_set_rate(), we get stuck in
propagate_rate().

Create a separate clock for nand, inheriting the rate of the aemif
clock and retrieve it in the davinci_nand module.

Cc: <stable@vger.kernel.org> # 4.9.x
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>