Sram 768 support

Dezaemon 3D support

it's using 3 normal 256kibit sram chips, that are mapped to
0x8000000 first chip (like normal sram/flashram)
0x8040000 second chip
0x8080000 third chip

256kibit -> 0x40000, so you should be able to read up to 0x8080000 in one 3x sram stream