Fixed first stage loader for SD2PSX

the following first-stage.mcd file has an update version of the SD2PSX first stage bootloader

With the following enhancements:

• does not search system update paths wich dont correspond to documented existent PS2 revisions
• Does not run SCPH-15000 Kernel patches by mistake on another models
• Supports PSX DESR
• Compiled on latest SDK instead of 2019 SDK