staging: comedi: gsc_hpdi: make board name pointer const

Change the type of the `name` member of `struct hpdi_board` from `char
*` to `const char *` as it should not be modifiable.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>