mfd: wm8xxx-core: Constify static struct resource

Constify a number of static struct resource. The only usage of the
structs are to assign their address to the resources field in the
mfd_cell struct. This allows the compiler to put them in read-only
memory. Done with the help of Coccinelle.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>