drm/i915: Detect if MIPI panel based on VBT and initialize only if present

It seems by default the VBT has MIPI configuration block as well. The
Generic driver will assume always MIPI if MIPI configuration block is found.
This is causing probelm when actually there is eDP. Fix this by looking
into general definition block which will have device configurations. From here
we can figure out what is the LFP type and initialize MIPI only if MIPI
is found.

v2: Addressed review comments by Damien
    - Moved PORT definitions to intel_bios.h and renamed as DVO_PORT_MIPIA
    - renamed is_mipi to has_mipi and moved definition as suggested
    - Check has_mipi inside parse_mipi and intel_dsi_init insted of outside

v3: Make has_mipi as a bitfield as suggested

Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
[danvet: fold in conditions to pack everything neatly below 80 chars.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>