snes: make pcx_to_compressed_tilemap_8bpp.c generic

It should now work for 4bpp tiles too
snes: make opening logo compressed

had to make the image full-screen width again
this makes the display not work right, known problem
snes: added generic palette load function

Uses DMA
snes: use common DMA loading routines

This makes loading the compressed tilemaps a bit more streamlined.