msm-fb-refresher: Perform ioctl even if there are errors

I noticed that some times the framebuffer driver gets configured in a way that the ioctl performed by msm-fb-refresher returns something lower than zero (see source).

For example when the Xorg starts I noticed it does a ioctl BLANK and UNBLANK, but if msm-fb-refresher performs a ioctl in that moment it stops its loop and exit.

For this reason I lost a lot of time trying to understand what was the problem with Xorg not displaying anything until I noticed that I had to restart the msm-fb-refresher.

Whit this change we don't have to care about msm-fb-refresher as it will continue call ioctl PAN even if the framebuffer returns some negative error code.