drm/i915/bios: calculate panel type as per child device index in VBT

Each LFP may have different panel type which is stored in LFP data
data block. Based on the child device index respective panel-type/
panel-type2 field will be used.

v1: Initial rfc verion.
v2: Based on review comments from Jani,
- Used panel-type instead addition panel-index variable.
- DEVICE_HANDLE_* name changed and placed before DEVICE_TYPE_*
macro.
v3:
- passing intel_bios_encoder_data as argument of
intel_bios_init_panel(). Passing NULL to indicate encoder is not
initialized yet for dsi as current focus is to enable dual EDP. [Jani]
v4:
- encoder->devdata used which is initialized before from vbt
structure. [Jani]

Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220620065138.5126-1-animesh.manna@intel.com