drm/edid: add drm_edid_get_product_id()

Add a struct drm_edid based function to get the vendor and product ID
from an EDID. Add a separate struct for defining this part of the EDID,
with defined byte order for manufacturer name, product code and serial
number.

v2: Define manufacturer_name as __be16 instead of u8[2] (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/df0e7dedbf7f2c190039d6e6eae3e126eba113c9.1712655867.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>