drm/i915/display: hide workaround for broken vbt in intel_bios.c

Instead of poluting the normal code path in intel_display.c, make
intel_bios.c handle the brokenness of the VBT.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210430223808.1078010-5-lucas.demarchi@intel.com