-In case yoffset is not set=0 by the driver (which seems to occur randomly on certain configurations), on next set_video_mode call screen freezes and cannot be updated. Condition to set yoffset to 0 if current value is >0 is added as fix.
-If setterm is not available, sh error occurs in the shell on gfx_ctx_mali_fbdev_destroy call. Condition based on setterm availability is added to avoid this.
-If pixclock from driver is not available (=0), divide by 0 occurs when trying to calculate refresh rate. Condition is added as a fix, if pixclock=0 refresh rate is set as 60.