drm/i915: Correct MIPI operation mode as per expected values from VBT

In VBT fields operation mode is 0 for Video mode and 1 for command mode.
This field will be directly used as is in generic panel driver. So
adjust accordingly.

Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>