ARM: shmobile: emev2: Use __initconst for const init definition

__initconst must be used instead of __initdata for
const init definitions.

This problem was introduced by 3d5de271 ("mach-shmobile: Emma
Mobile EV2 DT support V3") in v3.4-rc7.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>