drm/i915: Clean up intel_fbdev_init_bios() a bit

drm/i915: Clean up intel_fbdev_init_bios() a bit

Sort out the mess with the local variables in
intel_fbdev_init_bios(). Get rid of all aliasing pointers,
use standard naming/types, and introduce a few more locals
in the loops to avoid the hard to read long struct walks.

While at we also polish the debugs a bit to use the
canonical [CRTC:%d:%s] style.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210609085632.22026-6-ville.syrjala@linux.intel.com
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>