CdlGetmode is GetParam, fix it according to Mednafen's implementation

CdlGetmode is GetParam, fix it according to Mednafen's implementation

The result size for GetParam (previously Getmode) should be only 5 and done this way.

Here's Mednafen implementation :
https://github.com/libretro-mirrors/mednafen-git/blob/1899500078169e787f86eb5302a3f35abdaa8764/src/psx/cdc.cpp#L2095

Nocash's documentation also shows that our previous implementation was wrong :
https://problemkaputt.de/psx-spx.htm
(See CDROM Controller Command Summary section or CDROM - Status Commands)