ARM: davinci: make davinci_soc_info structures const

Make davinci_soc_info structures const as they are either passed to the
function davinci_common_init having the argument as const or their field
cpu_clks of type struct clk_lookup * is passed to the function
davinci_clk_init.

So, the fields are never modified and the structures can be const.

Done using Coccinelle.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
[nsekhar@ti.com: minor commit message adjustment]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>