power: supply: account for const type of of_device_id.data

This driver creates two const structures that it stores in the data
field of an of_device_id array.

The data field of an of_device_id structure has type const void *, so
there is no need for a const-discarding cast when putting const values
into such a structure.

Furthermore, adding const to the declaration of the location that
receives a const value from such a field ensures that the compiler
will continue to check that the value is not modified.  The
const-discarding cast on the extraction from the data field is thus
no longer needed.

Done using Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>