mfd: stmpe: Constify static struct resource

Constify a couple of static struct resource. The only usage of the
structs is 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>
Signed-off-by: Lee Jones <lee.jones@linaro.org>