tmio: Silence warnings introduced by mfd changes

This silences warnings such as

drivers/video/tmiofb.c: In function 'tmiofb_hw_init':
drivers/video/tmiofb.c:270: warning: initialization discards qualifiers from pointer target type

These were added by me in commit 2a79bb1d.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>