Actually, I just realized that if you uncheck "Savestate extra data -> Screenshot" in Settings -> Emulation, it saves uncompressed. RAM regions are here in the file:
- 0x19000 - 0x20FFF: IWRAM (0x03XXXXXX address space)
- 0x21000 - 0x60FFF: WRAM (0x02XXXXXX address space)